It seems that Amazon's Kindle ebook reader doesn't support the epub format. It would probably be a good idea to include another ebook format as well, like mobipocket.
Thanks for pointing me to that! I used it to convert the ePub to Mobi and added it to the repo.
For what it's worth, Calibre will convert it for you ( and manage your library. ) it's a bit of effort to use but its something you rarely have to use. http://calibre-ebook.com