Love this book. It is chock full of not only really neat spells and magic for your evil villains to utilize, but hundreds of story threads involving said spells.
One of my favorite examples:
Bone Blast is a first level spell that requires a bone from a still-living child as a material component. Now suppose the good-aligned characters of a party (heck, even the neutral-aligned ones!) find out that Evil Villain #121 is not only capable of casting said spell, but has a... errr.. stockpile of components to cast this spell. It doesn't take getting the girl, a sense of duty, or even treasure to motivate anyone worthy of the title "hero" to take down the Real Piece of Work responsible for this.
Past this, there are also fascinating prestige classes, some rather disgusting feats and magic items, and a very good discussion of evil motivations for NPCs.