Shadow Magic (Shadow Magic Series #1)

Thorn, an outlaw's son, wasn't supposed to be a slave. He's been sold to Tyburn, an executioner, and they're headed to Castle Gloom in Gehenna, the land of undead, where Thorn will probably be fed to a vampire. Lilith Shadow wasn't supposed to be ruler of Gehenna. But following the murder of her family, young Lily became the last surviving member of House Shadow, a long line of dark sorcerers. Her country is surrounded by enemies and the only way she can save it is by embracing her heritage...