DragonLancer
Adventurer
As DM I've used a couple of the demons from the book, one or two PrC's, a handful of spells and vile damage. I did run a one-shot evil adventure for my group and let them use the book which they greatly enjoyed.
Overall though, I think its a good book but it feels far too full of optional rules rather than good solid information on the nature of evil in D&D.
Overall though, I think its a good book but it feels far too full of optional rules rather than good solid information on the nature of evil in D&D.