Cursed Blood - Grimwood, #1

Zel has lived his entire life within the confines of a square mile of the forest. The tower is his refuge. The witch, his captor. Forced to do her bidding, he dreams of a day when he can leave the cursed place and be free. But fate has other plans and freedom can take many guises. As a girl, Geneva devoured stories about the wild boy who lived at the highest point in the forest. A changeling, a prince, a forest spirit-all the tales tell a different story.
Imagine her surprise when she stumbles across the cursed tower and the young man held prisoner there. It'll take all her cunning and courage to free him. What she doesn't know is that freeing him might doom them all.