To use, do:

python downloader.py [-f (epub|html|txt)] <url> 

Default format is epub.

Eg:

python downloader.py http://www.fanfiction.net/s/5192986/1/A_Fox_in_Tokyo

Do 'python downloader.py -h' for more options.

This tool uses Python 2.5.2, but should work with newer versions of Python.