These are a really good series of books. I have only read the firts 4 but they are totally awsome!!! Its about this guy who has a GF who is like, a witch in another world called the everworld. With vikings and everything. The girls name is Senna, and her bf, two guys, and her half sister April, get trapped in the same world when they try to save her. It is pretty gory, and very sexy.