I have used LaTex to write a few books. I usually use TexShop for OS X which uses XeTex so you get the unicode support, etc. Again, for the Mac, the Aquamacs version of Emacs has goot LaTex support built in, and is a good alternative to TexShop.
Your comment sounds like TeXShop only uses XeTeX, which is not true. TeXShop certainly has the option to use XeTeX, along with plain TeX, LaTeX, ConTeXt, and other variants. :-)
