Night Embrace - Sherrilyn Kenyon
The thing that compels me to read future books in the series is Acheron. I agree with lots of other reviewers that you lose interest about 1/2 through the book when you have to follow several characters, all similar and the mythology is confusing. I really gave up on trying to understand who everyone was and how they were related. And really, the ending is so predictable that I really didn't care. *shrugs*