Unraveller

A dark YA fantasy about learning to use your power and finding peace, from award-winning author Frances Hardinge
In a world where anyone can create a life-destroying curse, only one person has the power to unravel them.
Kellen does not fully understand his talent, but helps those transformed maliciously—including Nettle. Recovered from entrapment in bird form, she is now his constant companion and closest ally.
But Kellen has also been cursed, and unless he and Nettle can remove his curse, Kellen is in danger of unravelling everything—and everyone—around him . . .