GitBook: Write Books using Markdown on OpenShift by Marek Jelen.
From the post:
GitBook is a tool for using Markdown to write books, which are converted to dynamic websites or exported to static formats like PDF. GitBook also integrates with Git and GitHub, adding a social element to the book creation process.
If you are exporting your book into an HTML page, interactive aspects are also embedable. At the time of this writing, the system provides support for quizzes and JavaScript exercises. However, the tool is fully open source and written using Node.js, so you are free to extend the functionality to meet your needs.
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The Gitbook Learn Javascript is used as an example of production with GitBook.
It’s readable but in terms of the publishing craft, the Mikraot Gedolot or The Art of Computer Programming (TAOCP), it’s not.
Still, it may be useful for one-off exports from topic maps and other data sources.