Emacs is a great tool for book editing and writing. I used reStructuredText text but Markdown, ASCIIDoc, Docbook or any number of formats would work equally well. Emacs’s ediff is a powerful diffing tool that made it possible for me to track the changes made by the proofreader and selectively apply, but also edit, the changes she made before committing them to the original manuscript. I think that feature alone made it worth writing it in Emacs.
— How to write a book in Emacs, Mickey Petersen @ Mastering Emacs
A nice description of how reStructuredText and pandoc can be used in a publishing workflow.