Not sure what your prior experience is in this matter, but here are my general thoughts on book writing.

I have written, or been involved in the writing of, a few books. My e pertain every was that it is easier to start a book from the TOC.

I am assuming you will be using LaTex or something similar? Writing a book in anything other than a structured writing environment can be hell. Certainly avoid ms word like a cockroach should avoid a hammer.