diff --git a/src/pyj/read_book/comm.pyj b/src/pyj/read_book/comm.pyj
new file mode 100644
index 0000000000..7da6c4731b
--- /dev/null
+++ b/src/pyj/read_book/comm.pyj
@@ -0,0 +1,144 @@
+# vim:fileencoding=utf-8
+# License: GPL v3 Copyright: 2017, Kovid Goyal <kovid at kovidgoyal.net>
+from __python__ import bound_methods, hash_literals
+
+from aes import GCM
+
+from book_list.globals import main_js, get_translations
+from book_list.theme import get_font_family
+from dom import ensure_id
+
+
+LOADING_DOC = '''
+<!DOCTYPE html>
+<html>
+<head>
+<meta name="viewport" content="width=device-width, initial-scale=1, user-scalable=no">
+<meta http-equiv="X-UA-Compatible" content="IE=edge">
+<script type="text/javascript" id="bootstrap">
+window.iframe_type = '__IFRAME_TYPE__';  // different in different iframes
+__SCRIPT__
+end_script
+</head>
+<body style="font-family: __FONT__">
+<div style="font-size:larger; font-weight: bold; margin-top:48vh; text-align:center">
+__BS__
+</div>
+</body>
+</html>
+'''.replace('end_script', '<' + '/script>')  # cannot have a closing script tag as this is embedded inside a script tag in index.html
+
+
+def iframe_js():
+    if not iframe_js.ans:
+        iframe_js.ans = main_js().replace(/is_running_in_iframe\s*=\s*false/, 'is_running_in_iframe = true')
+        main_js(None)
+    return iframe_js.ans
+
+
+class Messenger:
+
+    def __init__(self):
+        self.secret = Uint8Array(64)
+
+    def reset(self):
+        window.crypto.getRandomValues(self.secret)
+        self.gcm_to_iframe = GCM(self.secret.subarray(0, 32))
+        self.gcm_from_iframe = GCM(self.secret.subarray(32))
+
+    def encrypt(self, data):
+        return self.gcm_to_iframe.encrypt(JSON.stringify(data))
+
+    def decrypt(self, data):
+        return JSON.parse(self.gcm_from_iframe.decrypt(data))
+
+
+class IframeWrapper:
+
+    def __init__(self, handlers, iframe, iframe_type, bootstrap_text):
+        self.messenger = Messenger()
+        self.iframe_id = ensure_id(iframe, 'content-iframe')
+        self.needs_init = True
+        self.ready = False
+        self.encrypted_communications = False
+        self.srcdoc_created = False
+        self.iframe_type = iframe_type
+        self.bootstrap_text = bootstrap_text
+        self.handlers = {k: handlers[k] for k in handlers}
+        self.on_ready_handler = self.handlers.ready
+        self.handlers.ready = self.on_iframe_ready
+        window.addEventListener('message', self.handle_message, False)
+
+    @property
+    def iframe(self):
+        return document.getElementById(self.iframe_id)
+
+    def create_srcdoc(self):
+        r = /__([A-Z][A-Z_0-9]*[A-Z0-9])__/g
+        data = {
+            'BS': self.bootstrap_text,
+            'SCRIPT': iframe_js(),
+            'FONT': get_font_family(),
+            'IFRAME_TYPE': self.iframe_type,
+        }
+        self.iframe.srcdoc = LOADING_DOC.replace(r, def(match, field): return data[field];)
+        self.srcdoc_created = True
+
+    def init(self):
+        if not self.needs_init:
+            return
+        self.needs_init = False
+        iframe = self.iframe
+        if self.srcdoc_created:
+            sdoc = iframe.srcdoc
+            iframe.srcdoc = '<p>&nbsp;</p>'
+            iframe.srcdoc = sdoc
+        else:
+            self.create_srcdoc()
+
+    def reset(self):
+        self.ready = False
+        self.needs_init = True
+        self.encrypted_communications = False
+
+    def _send_message(self, action, encrypted, data):
+        data.action = action
+        msg = {'data':data, 'encrypted': encrypted}
+        if encrypted:
+            msg.data = self.messenger.encrypt(data)
+        self.iframe.contentWindow.postMessage(msg, '*')
+
+    def send_message(self, action, **data):
+        self._send_message(action, self.encrypted_communications, data)
+
+    def send_unencrypted_message(self, action, **data):
+        self._send_message(action, False, data)
+
+    def handle_message(self, event):
+        if event.source is not self.iframe.contentWindow:
+            return
+        data = event.data
+        if self.encrypted_communications:
+            try:
+                data = self.messenger.decrypt(data)
+            except Exception as e:
+                print('Could not process message from iframe:')
+                console.log(e)
+                return
+        func = self.handlers[data.action]
+        if func:
+            func(data)
+        else:
+            print('Unknown action in message from iframe to parent: ' + data.action)
+
+    def on_iframe_ready(self, data):
+        self.messenger.reset()
+        msg = {'secret': self.messenger.secret, 'translations': get_translations()}
+        self.ready = True
+        callback = None
+        if self.on_ready_handler:
+            callback = self.on_ready_handler(msg)
+        self._send_message('initialize', False, msg)
+        self.encrypted_communications = True
+        if callback:
+            callback()
diff --git a/src/pyj/read_book/content_popup.pyj b/src/pyj/read_book/content_popup.pyj
index e06f4ad14b..8c7b9b2693 100644
--- a/src/pyj/read_book/content_popup.pyj
+++ b/src/pyj/read_book/content_popup.pyj
@@ -52,6 +52,10 @@ def __init__(self, view):
     def container(self):
         return document.getElementById('book-content-popup-overlay')
 
+    @property
+    def iframe(self):
+        return self.container.querySelector('iframe')
+
     @property
     def is_visible(self):
         return self.container.style.display is not 'none'
@@ -91,4 +95,3 @@ def show_footnote(self, data):
         c.style.width = f'{width}vw'
         header = c.firstChild
         self.create_footnote_header(header)
-        # iframe = c.lastChild
diff --git a/src/pyj/read_book/globals.pyj b/src/pyj/read_book/globals.pyj
index 8977cf6691..e30b25651f 100644
--- a/src/pyj/read_book/globals.pyj
+++ b/src/pyj/read_book/globals.pyj
@@ -2,7 +2,7 @@
 # License: GPL v3 Copyright: 2016, Kovid Goyal <kovid at kovidgoyal.net>
 from __python__ import hash_literals
 
-from aes import GCM, random_bytes
+from aes import random_bytes
 from encodings import hexlify
 from gettext import gettext as _, register_callback, gettext as gt
 
@@ -19,24 +19,6 @@ def current_book():
     return current_book.book
 current_book.book = None
 
-class Messenger:
-
-    def __init__(self):
-        self.secret = Uint8Array(64)
-
-    def reset(self):
-        window.crypto.getRandomValues(self.secret)
-        self.gcm_to_iframe = GCM(self.secret.subarray(0, 32))
-        self.gcm_from_iframe = GCM(self.secret.subarray(32))
-
-    def encrypt(self, data):
-        return self.gcm_to_iframe.encrypt(JSON.stringify(data))
-
-    def decrypt(self, data):
-        return JSON.parse(self.gcm_from_iframe.decrypt(data))
-
-messenger = Messenger()
-iframe_id = 'read-book-iframe'
 uid = 'calibre-' + hexlify(random_bytes(12))
 
 def viewport_mode_changer(val):
diff --git a/src/pyj/read_book/iframe.pyj b/src/pyj/read_book/iframe.pyj
index 6104f8deb8..eb69a6b154 100644
--- a/src/pyj/read_book/iframe.pyj
+++ b/src/pyj/read_book/iframe.pyj
@@ -426,6 +426,7 @@ def find(self, data, from_load):
                 self.send_message('find_in_spine', text=data.text, backwards=data.backwards, searched_in_spine=data.searched_in_spine)
 
 def init():
-    script = document.getElementById('bootstrap')
-    script.parentNode.removeChild(script)  # free up some memory
-    IframeBoss()
+    if window.iframe_type is 'main':
+        script = document.getElementById('bootstrap')
+        script.parentNode.removeChild(script)  # free up some memory
+        IframeBoss()
diff --git a/src/pyj/read_book/view.pyj b/src/pyj/read_book/view.pyj
index dd06f2a615..fdbbc2e35e 100644
--- a/src/pyj/read_book/view.pyj
+++ b/src/pyj/read_book/view.pyj
@@ -6,15 +6,14 @@
 from gettext import gettext as _
 
 from ajax import ajax_send
-from book_list.globals import get_session_data, get_translations, main_js
+from book_list.globals import get_session_data
 from book_list.router import push_state, read_book_mode
-from book_list.theme import get_color, get_font_family
-from dom import add_extra_css, build_rule, set_css, svgicon
+from book_list.theme import get_color
+from dom import add_extra_css, build_rule, set_css, svgicon, unique_id
 from modals import error_dialog, warning_dialog
+from read_book.comm import IframeWrapper
 from read_book.content_popup import ContentPopupOverlay
-from read_book.globals import (
-    current_book, iframe_id, messenger, set_current_spine_item
-)
+from read_book.globals import current_book, set_current_spine_item
 from read_book.goto import get_next_section
 from read_book.overlay import Overlay
 from read_book.prefs.colors import resolve_color_scheme
@@ -26,26 +25,6 @@
 from session import get_device_uuid, get_interface_data
 from utils import html_escape, is_ios, parse_url_params, username_key
 
-LOADING_DOC = '''
-<!DOCTYPE html>
-<html>
-<head>
-<meta name="viewport" content="width=device-width, initial-scale=1, user-scalable=no">
-<meta http-equiv="X-UA-Compatible" content="IE=edge">
-<script type="text/javascript" id="bootstrap">
-window.iframe_type = '__IFRAME_TYPE__';  // different in different iframes
-__SCRIPT__
-end_script
-</head>
-<body style="font-family: __FONT__">
-<div style="font-size:larger; font-weight: bold; margin-top:48vh; text-align:center">
-__BS__
-</div>
-</body>
-</html>
-'''.replace('end_script', '<' + '/script>')  # cannot have a closing script tag as this is embedded inside a script tag in index.html
-
-
 add_extra_css(def():
     sel = '.book-side-margin'
     ans = build_rule(sel, cursor='pointer', color='rgba(0, 0, 0, 0)', text_align='center', height='100vh', user_select='none', display='flex', align_items='center', justify_content='center')
@@ -118,6 +97,7 @@ def __init__(self, container, ui):
         set_left_margin_handler(left_margin)
         right_margin = E.div(svgicon('caret-right'), style='width:{}px;'.format(sd.get('margin_right', 20)), class_='book-side-margin', id='book-right-margin', onclick=self.right_margin_clicked)
         set_right_margin_handler(right_margin)
+        iframe_id = unique_id('read-book-iframe')
         container.appendChild(
             E.div(style='max-height: 100vh; width: 100vw; height: 100vh; overflow: hidden; display: flex; align-items: stretch',  # container for horizontally aligned panels
                   E.div(style='max-height: 100vh; display: flex; flex-direction: column; align-items: stretch; flex-grow:2',  # container for iframe and any other panels in the same column
@@ -137,15 +117,7 @@ def __init__(self, container, ui):
                 )
             )
         )
-        self.search_overlay = SearchOverlay(self)
-        self.content_popup_overlay = ContentPopupOverlay(self)
-        self.overlay = Overlay(self)
-        self.processing_spine_item_display = False
-        self.iframe_ready = False
-        self.pending_load = None
-        self.encrypted_communications = False
-        window.addEventListener('message', self.handle_message, False)
-        self.handlers = {
+        handlers = {
             'ready': self.on_iframe_ready,
             'error': self.on_iframe_error,
             'next_spine_item': self.on_next_spine_item,
@@ -162,21 +134,27 @@ def __init__(self, container, ui):
             'show_footnote': self.on_show_footnote,
             'print': self.on_print,
         }
+        self.iframe_wrapper = IframeWrapper(handlers, document.getElementById(iframe_id), 'main', _('Bootstrapping book reader...'))
+        self.search_overlay = SearchOverlay(self)
+        self.content_popup_overlay = ContentPopupOverlay(self)
+        self.overlay = Overlay(self)
+        self.processing_spine_item_display = False
+        self.pending_load = None
         self.currently_showing = {}
 
     @property
     def iframe(self):
-        return document.getElementById(iframe_id)
+        return self.iframe_wrapper.iframe
 
     def left_margin_clicked(self, event):
         if event.button is 0:
             event.preventDefault(), event.stopPropagation()
-            self.send_message('next_screen', backwards=True)
+            self.iframe_wrapper.send_message('next_screen', backwards=True)
 
     def right_margin_clicked(self, event):
         if event.button is 0:
             event.preventDefault(), event.stopPropagation()
-            self.send_message('next_screen', backwards=False)
+            self.iframe_wrapper.send_message('next_screen', backwards=False)
 
     def top_margin_clicked(self, event):
         if event.button is 0:
@@ -184,7 +162,7 @@ def top_margin_clicked(self, event):
             self.show_chrome()
 
     def forward_gesture(self, gesture):
-        self.send_message('gesture_from_margin', gesture=gesture)
+        self.iframe_wrapper.send_message('gesture_from_margin', gesture=gesture)
 
     def iframe_size(self):
         iframe = self.iframe
@@ -198,13 +176,13 @@ def on_request_size(self, data):
         # On iOS/Safari window.innerWidth/Height are incorrect inside an iframe
         window.scrollTo(0, 0)  # ensure the window is at 0 because otherwise it sometimes moves down a bit on mobile thanks to the disappearing nav bar
         w, h = self.iframe_size()
-        self.send_message('window_size', width=w, height=h)
+        self.iframe_wrapper.send_message('window_size', width=w, height=h)
 
     def on_print(self, data):
         print(data.string)
 
     def find(self, text, backwards):
-        self.send_message('find', text=text, backwards=backwards, searched_in_spine=False)
+        self.iframe_wrapper.send_message('find', text=text, backwards=backwards, searched_in_spine=False)
 
     def on_find_in_spine(self, data):
         if data.searched_in_spine:
@@ -225,7 +203,7 @@ def on_find_in_spine(self, data):
             if found_in:
                 self.show_name(found_in, initial_position={'type':'search', 'search_data':data, 'replace_history':True})
             else:
-                self.send_message('find', text=data.text, backwards=data.backwards, searched_in_spine=True)
+                self.iframe_wrapper.send_message('find', text=data.text, backwards=data.backwards, searched_in_spine=True)
         )
 
     def bump_font_size(self, data):
@@ -287,67 +265,9 @@ def side_margin(which, val):
             m.firstChild.style.height = val + 'px'
         side_margin('left', margin_left), side_margin('right', margin_right)
 
-    def create_src_doc(self):
-        iframe_script = main_js().replace(/is_running_in_iframe\s*=\s*false/, 'is_running_in_iframe = true')
-        main_js(None)
-        r = /__([A-Z][A-Z_0-9]*[A-Z0-9])__/g
-        self.main_srcdoc = def():
-            data = {
-                'BS': _('Bootstrapping book reader...'),
-                'SCRIPT': iframe_script,
-                'FONT': get_font_family(),
-                'IFRAME_TYPE': 'main'
-            }
-            return LOADING_DOC.replace(r, def(match, field): return data[field];)
-
-    def init_iframe(self):
-        if self.main_srcdoc is None:
-            return
-        if not self.main_srcdoc:
-            self.create_src_doc()
-        self.encrypted_communications = False
-        self.iframe.srcdoc = self.main_srcdoc()
-        self.main_srcdoc = None
-
-    def reset_iframe(self):
-        # Reset the iframe to ensure that all state from previous books is
-        # cleared
-        self.iframe_ready = False
-        if self.main_srcdoc is None:
-            self.main_srcdoc = def():
-                return self.iframe.srcdoc
-
-    def send_message(self, action, **data):
-        data.action = action
-        msg = {'data':data, 'encrypted':self.encrypted_communications}
-        if self.encrypted_communications:
-            msg.data = messenger.encrypt(data)
-        self.iframe.contentWindow.postMessage(msg, '*')
-
-    def handle_message(self, event):
-        if event.source is not self.iframe.contentWindow:
-            return
-        data = event.data
-        if self.encrypted_communications:
-            try:
-                data = messenger.decrypt(data)
-            except Exception as e:
-                print('Could not process message from iframe:')
-                console.log(e)
-                return
-        func = self.handlers[data.action]
-        if func:
-            func(data)
-        else:
-            print('Unknown action in message from iframe to parent: ' + data.action)
-
     def on_iframe_ready(self, data):
-        messenger.reset()
-        w, h = self.iframe_size()
-        self.send_message('initialize', secret=messenger.secret, translations=get_translations(), width=w, height=h)
-        self.encrypted_communications = True
-        self.iframe_ready = True
-        self.do_pending_load()
+        data.width, data.height = self.iframe_size()
+        return self.do_pending_load
 
     def do_pending_load(self):
         if self.pending_load:
@@ -404,7 +324,7 @@ def display_book(self, book):
         self.hide_overlays()
         is_current_book = self.book and self.book.key == book.key
         if not is_current_book:
-            self.reset_iframe()
+            self.iframe_wrapper.reset()
         self.book = current_book.book = book
         self.ui.db.update_last_read_time(book)
         self.loaded_resources = {}
@@ -474,7 +394,7 @@ def goto_bookpos(self, bookpos):
 
     def goto_named_destination(self, name, frag):
         if self.currently_showing.name is name:
-            self.send_message('scroll_to_anchor', frag=frag)
+            self.iframe_wrapper.send_message('scroll_to_anchor', frag=frag)
         else:
             spine = self.book.manifest.spine
             idx = spine.indexOf(name)
@@ -548,23 +468,21 @@ def on_update_toc_position(self, data):
     def show_spine_item(self, resource_data):
         self.loaded_resources = resource_data
         self.pending_load = resource_data
-        if self.iframe_ready:
+        if self.iframe_wrapper.ready:
             self.do_pending_load()
         else:
-            self.init_iframe()
+            self.iframe_wrapper.init()
 
     def show_spine_item_stage2(self, resource_data):
         self.currently_showing.loading = False
         # We cannot encrypt this message because the resource data contains
         # Blob objects which do not survive encryption
-        self.encrypted_communications = False
         self.processing_spine_item_display = True
-        self.send_message('display',
+        self.iframe_wrapper.send_unencrypted_message('display',
             resource_data=resource_data, book=self.book, name=self.currently_showing.name,
             initial_position=self.currently_showing.initial_position,
             settings=self.currently_showing.settings,
         )
-        self.encrypted_communications = True
 
     def on_content_loaded(self, data):
         self.processing_spine_item_display = False
@@ -574,8 +492,8 @@ def on_content_loaded(self, data):
         window.scrollTo(0, 0)  # ensure window is at 0 on mobile where the navbar causes issues
 
     def update_font_size(self):
-        self.send_message('change_font_size', base_font_size=get_session_data().get('base_font_size'))
+        self.iframe_wrapper.send_message('change_font_size', base_font_size=get_session_data().get('base_font_size'))
 
     def update_color_scheme(self):
         cs = self.get_color_scheme(True)
-        self.send_message('change_color_scheme', color_scheme=cs)
+        self.iframe_wrapper.send_message('change_color_scheme', color_scheme=cs)
