kelly,
It depends what you're looking for, exactly.
If you're after a book featuring stunning photos of the world's great golf courses and commentary on those courses and clubs, pick up Darius Oliver's and David Scalletti's new, Planet Golf. If you're after an education in golf architecture, you can't go wrong with Tom Doak's, The Anatomy of a Golf Course.
I'd add any, and all, of Geoff Shackelford's books to the list too.