Merrick (The Vampire Chronicles, #7) by Anne Rice

Louis is a vampire tortured by guilt. His status as a killer has left him conflicted for much of his immortal life, but after the murder of Claudia, his beloved child vampire, he spirals into a state of depression. And in a moment of desperation he decides to bring her back with the help of the beautiful witch Merrick. To save Louis' sanity, Merrick must use black magic to call up the ghost of Claudia - however dangerous this may be. But in the dark unknown of the underworld there are other spirits who will not lie still, and her search takes her close to the edge of peril.