I ended up using MS Word for the ugly monkey book, because O'Reilly only offered me that or LaTex, and I didn't want the hassle of figuring out the latter, which I'd never used. It worked out okay; I just used their template, and made a point of religiously applying the styles they'd set up. And yeah, I kept copies of the Word files (one per chapter) in revision control, though I don't think I ever used that for anything other than backup purposes.
The biggest lesson I gained from it was that while outlining and proposing a book is exciting, and getting it accepted by the publisher was really exciting, actually writing the thing was way more work than I'd expected. I'd written and edited professionally for years in the magazine business, so the writing part was familiar, but the difference between a 3,000-word article and a 500-page book turned out to be much bigger in practice than it had looked in theory. Especially late in the process, when it was all about plowing through everything again to get it all to the highest possible standard, the book was a huge undertaking.
It didn't sell particularly well, which was a disappointment, but the fact that I had believed (and continue to believe) in the book's premise made it possible for me to invest the work required. And in hindsight, I think of the book as a success, at least for me personally. Not because it sold a lot of copies, but because the process of writing it taught me more about its subject matter than I could have learned any other way.
I never would have finished it if I hadn't been sustained by my naive hopes of big sales, and I'm glad I wrote it, so I guess I'm glad I was naive. Presumably you have high hopes for your own book. That's great. Hang onto those. They will be essential as you close in on completion, and the mountain of remaining work just seems to reach higher and higher.
Good luck!