There are not prestige classes for every god. I sort of wish there were, honestly, but we didn't have the space for that sort of thing and the folks who planned what was going to be in the book wanted to keep some of the prestige classes more general (which is something I do agree with, as it means more utility for everyone).
There's not a lot of "recovered ground" in the F&P prestige classes. For instance, you _won't_ see versions of the divine seeker, divine champion, etc. as ruleslawyer suggests in his last post.
As someone upthread said, and as Rich Baker has confirmed elsewhere on the net, the book includes full write-ups (about the size of those in Deities & Demigods, but maybe a little longer because both Eric Boyd and I tend to write "long") of the 30 "core" FR gods that appear in the FRCS. It includes FRCS write ups of pretty much every other deity that appeared in the three second edition god books, as well as a few who never appeared in those books. There are also some temples with maps and tons of story hooks.
I haven't seen the final version, so I can't speak as to how much crossover there is with Deities & Demigods insofar as salient divine abilities goes, but my guess would be that the book contains as little of that information as possible while still making it possible to use F&P without owning Deities & Demigods.
Someone upthread asked what I'd done for the book. Minus the biolerplate rules stuff and lists of gods, which were done in-house by the FR design team, I did about a third of the book. I think I covered 11 of the core gods (this is from memory, so it may be more or less than that), including Azuth, Selune, Shar, Tyr, Torm, Bane, Chauntea, Tymora and a few others. I did five or six prestige classes, about a half dozen of the small write-ups of human gods (Garagos and Denier for sure) and all the halfling and dwarf gods. I also designed one of the temples, associated with one of the deities in the above list. It's probably the "darkest" of all the temples in the book and one of the nastiest things I've written yet, but I've only skimmed the three or four temples Eric Boyd did.
I'm eager for the book to come out. I think my stuff is pretty good, and Eric's material ought to make long-time Realms fans drool with delight. The art is absolutely top notch, a step above even our best looking books (in my opinion, at least). Designing a book with such intensive number crunching was tedious in the extreme, but the "ideas" part of the project was really fun and rewarding. I'm proud to have my name on that book, and eagerly await the online reaction to some of the little bombs we planted in our text.
Erik