http://www.shareable.net/blog/how-to-create-an-ebook-the-open-source-way

« This guide explains one method for creating electronic books (« eBooks ») in the ePub format using open source tools available on most popular computing platforms. ePub is the International Digital Publishing Forum’s open standard for digital book publishing, and most major electronic reading devices support it (except for the Kindle—sorry, Amazon fans!). But more importantly, formatting an electronic book as an ePub guarantees that many online eBook marketplaces will host and distribute the work. »