You may think that Git and GitHub are just for writing code. For the most part, you'd be right. Git and GitHub revolutionized programming, making it super easy to manage and store revisions of projects when writing code. But GitHub stands to revolutionize the revision and management of writing something other than code: books.
This article on GitHub Teaching is the central repository of all of the techniques developed by Matthew McCullough, VP of Training at GitHub, and all other committers visible in the repo history--and that illustrates what is so revolutionary about this idea.
Version Control for Books
The article linked to above can be thought of as a book about writing books on GitHub, which itself exhibits all of the virtues of open-source book authorship on GitHub. You can see who has committed content to the book, which pieces of content were authored by whom, and who has edited it.
Writing a book with GitHub (be it technical, non-fiction, or even fiction) is completely unlike any writing practice extolled by writers for centuries. Any book written on GitHub would not be the life's work of an individual locked up in a cabin somewhere pouring his soul onto a keyboard, to produce a manuscript not to be seen by anyone but his agent and editor before publication.
A book written on GitHub would be open source, published immediately all over the world and constantly evolving. It would have as many authors as committed to the project, and always open to revisions and re-revisions.
Any book written on GitHub would be open source, thus no individual could take ownership of the book in order to make a profit, and there's the rub--would any book written on GitHub be worth reading if no one could truly take ownership of the project? Perhaps that's why we don't see many book repos forked on GitHub ...
What do you think? Is GitHub a viable platform for book authorship? Could Git be used to write multi-authored, version-controlled books not only about technical subjects and programming, but also of fiction? Would you feel comfortable committing to a book repo if it was on a subject with which you were familiar?