Adobe Indesign is pretty much the *de facto* industry standard for book layout when text and graphics need to be incorporated together. It's used for everything from RPG books to textbooks, and it's $19.99 US per month (about $240 US every year).

Of course, there are a lot of alternatives, both commercial and non-commercial. I personally like Scribus, but there are other possibilities here: http://alternativeto.net/software/adobe-indesign/