The Boy Who Lost Fairyland — Catherynne M. Valente

When a young troll named Hawthorn is stolen from Fairyland by the Red Wind, he becomes a changeling-a human boy-in the strange city of Chicago, a place no less bizarre and magical than Fairyland. Left with a human family, Hawthorn struggles with his troll nature and his changeling fate, while attending school and learning about human kindnesses-and un-kindnesses.