Publisher's Weekly has a great run-down of the rapidly growing genre of paranormal romance books, spearheaded by authors like Sherrilyn Kenyon. Among other things, it explains the difference between paranormal romance and dark fantasy — paranormal romance is about the relationship, dark fantasy is usually about other stuff — and illuminates debates over whether a book can be paranormal romance if the couple doesn't end up together. Also, paranormal romance is more than vampires: there are werewolves and other monsters as well. Most of all, it's amazing to realize quite how successful the genre has become, growing at a massive rate even as the book industry as a whole suffers.