I recently read an article about Booktype, got interested and tried software myself.

Booktype is developed by Sourcefabric, a non profit organization that provides couple of other interesting solutions like Airtime (radio automation), Newscoop (content management system) and Superdesk which combines Airtime with Newscoop as a suite for independent media.

<p>
  Booktype uses <a href="https://www.djangoproject.com/">Django</a> web framework. Software is easy to install but you can&#8217;t forget about <a href="http://booki-dev.flossmanuals.net/git?p=objavi2.git">Objavi 2</a> (FLOSS Manuals book exporter) to save your work in any of the available format.
</p>

<p>
  Interface is simple and readable built with collaboration in mind. Each book has its own history, custom versions and permissions. Books are written in HTML using <a href="http://www.tinymce.com">TinyMCE</a> editor and can be exported to PDF, ODT, EPUB and MOBI format.
</p>