From the publisher:
Where reality ends, fantasy starts and at the heart of fantasy lies monsters. Roaming bands of mercenary monsters run along side their human and elven compatriots, searching out adventure and making names for themselves. Orcs, minotaurs, and all the rest are packed into one book. And now that you have Evil, GMs can run full monster campaigns. Details about monster culture, psychology, and adventuring provide GMs and PCs with enough information to run an entire party of trolls, ogres, ettins, orcs, goblins, and more. Rules for mixed races, new feats, and skills only monsters know. New prestige classes, rules for PC monster races, and new magic await.