In oppostion to other answers here I really recommend to spent a few days to prepare a framework in LaTeX.
Think twice about your workflow and the technical tools you need.
For example, how will you leave comments and annotations for yourself? How do you delete them? I usually write them into the margin in small red print and use the
marginfix package. To this end I define a new command, simply something like
\Anm (German abbrev. for comment).
Will you need a comparison between versions? Or even different versions? Take a day to become familiar with a version system. I'm using
git and to build comparisons between versions the script
latexdiff-git. A version system may help a lot in case you get stuck and you need to return to a earlier version.
scrbook to memoir, because KOMA-script adopts the european way to typeset, and for many more reasons.
To speed up compilation have a look at
And the most important thing: Employ
\ref as much as possible for any reference. Learn how to use
Zotero or whatever way to manage your bibliography! Probably you should prefer BibLaTeX to BibTeX.
Which encoding? utf-8 probably, but however, do not mix encondings, choose one which is sufficient for all kind of texts in your book.
Don't use LuaTeX or XeTeX for a serious project. LuaTeX simply is buggy and slow. pdfTeX still is the engine, for many years. There hasn't been a new LuaTeX version for a year!
How do you handle updates / upgrades of texlive or MikTeX? The former maintainer of the Libertine package one day published an incompatible update and after receiving some unfriendly comments withdrew from maintaining the package, leaving me behind with broken files. So it would be advisable to have way to test your monthly update before you encounter a lot of stress.
How will you backup your work consistently, inhouse and somewhere else?
I could go on writing, but I think you got the message: Think intensly on each step of your workflow at the beginning.
Edit due to comments below:
As user pmav99 argues, if you use non latin fonts, XeTeX is very helpfull. I agree with that; I was too narrow minded on the disadvantages of XeTeX. There surely are advantages which may justify using XeTeX »in a serious project«.
Edit three years later:
LuaTeX became a bit faster, but on a windows machine is much slower than pdftex, still. BibLaTeX and Biber are state of the art. And for the rest of my answer: no change.