I don't know what kind of books you're writing, but 100,000 pages is too many pages. Did you mean 100,000 words?

I've only ever written 50,000 word NaNoWriMo stuff, but I've had a lot of success with text files, simply marked-up, in emacs. One text file per chapter. A short Python script converts them into LaTeX and a makefile builds a PDF. All the notes are handled with org-mode. It's a really sweet setup.