Saint Death's Herald - C. S. E. Cooney

Lanie Stones is the necromancer that Death has been praying for. Heartbroken, exiled from her homeland as a traitor, Lanie Stones would rather take refuge in good books and delicate pastries than hunt a deathless abomination, but that is the duty she has chosen. The abomination in question happens to be her own great-grandfather, the powerful necromancer Irradiant Stones. Grandpa Rad has escaped from his prison and stolen a body, and is heading to the icy country of Skakhmat where he died, to finish the genocide he started. Fortunately for her, Lanie has her powerful death magic, including the power to sing the restless dead to their eternal slumber; and she has her new family by her side. Grandpa Rad may have finally met his match.