The Sable Moon

A headstrong young prince, enslaved far from home, must rescue his imperiled kingdom and those he loves from an ancient dark sorcery in Nancy Springer's magnificent third entry in the Book of Isle
The life of young Prince Trevyn of Isle changes forever on the day a mysterious boy named Gwern is welcomed without question into the family's castle. Stubborn and resentful of the unwanted intrusion, the errant teenage prince abandons his home and soon finds himself both in love and in jeopardy. Enraptured by the village girl Meg, he incurs the wrath of Wael, a powerful warlock, by saving the lady of his heart and her people from certain destruction.
But young Trevyn's trials have only just begun. Lured across the seas by his vengeful foe, he is captured and enslaved, and must somehow find his way to freedom. For the unprotected Isle is now at Wael's mercy, and love will surely die if the boy-prince cannot return to the realm as its champion.
A...