Ward Against Death by Melanie Card
Chronicles of a Reluctant Necromancer #1
Twenty-year-old Ward de Ath expected this to be a simple job - bring a nobleman's daughter back from the dead for fifteen minutes, let her family say good-bye, and launch his fledgling career as a necromancer. Goddess knows he can't be a surgeon - the Quayestri already branded him a criminal for trying so bringing people back from the dead it is.
But when Ward wakes the beautiful Celia Carlyle, he gets more than he bargained for. Insistent that she's been murdered, Celia begs Ward to keep her alive and help her find justice. By the time she drags him out her bedroom window and into the sewers, Ward can't bring himself to break his damned physician's Oath and desert her.
However, nothing is as it seems including Celia. One second, she's treating Ward like sewage, the next she's kissing him. And for a nobleman's daughter, she sure has a lot of enemies. If he could just convince his heart to give up on the infuriating beauty, he might get out of this alive...