Demon from the Dark by Kresley Cole

Tormented by his sordid past and racked by vampiric hungers, Malkom Slaine is pushed to the brink by the green-eyed beauty under his guard. Carrow Graie is hiding her own sorrows, until she meets a tortured warrior worth saving. But, in order for Malkom and Carrow to survive, he must unleash both the demon and vampire inside him.