Castles & Crusades actually has a number of monster books. Each has a slightly different focus. This one focuses on the game world of Aihrde. The Castles & Crusades Monster stat block is a nice combination of Basic's simplicity, 1st AD&D's comprehensiveness, and some 3.x style rules. Saves are simple (Physical, Mental or both), AC is ascending and there is a "Challenge Rating" stat and XP all factored in. Honestly it really is a synthesis of the best of D&D. Grabbing a monster from another source and converting on the fly really could not be easier.
At first I was not going to get this book. I had all three of the other monster books and this one seemed a bit redundant. But this one had something the others didn't; Demons and Devils. I don't want to say that this is the only reason I got it, but they were conspicuously absent from all the other books. Of course this book has more, a lot more, than just that.
I did enjoy all the new dragons and like it's "parent" book, this book has a bunch of new treasure.
Some of the monsters are world specific, but nothing that can't be worked around. In truth most of these monsters are all brand new to me and that is worth the price of the book alone. Even most of the demons, devils and dragons are new. Likewise for the treasure.