The Warcraft setting is fully D&D3.5 compatible. It, er, kinda says it right on the books. Everquest is OGL-only. The monsters in the Manual of Monsters are just monsters from the Warcraft setting. So, it's like the Creature Collections, Fiend Folio, or what have you. Sure, some may have the same names as "official" D&D monsters, but the stats are totally compatible. It just depends on if you want Warcraft-flavored monsters or if you play in the Warcraft setting. If you wanted, you could replace your Monster Manual with this book and have no problems. But, I'm not saying to do that.
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