Sky's End (Above the Black Book 1)

Details: Exiled to live as a Low, sixteen-year-old Conrad refuses to become heir to his murderous uncle. But Meritocracy is a harsh and unforgiving rule on the floating island of Holmstead, and when his ailing mother is killed by monstrous gorgantauns, Conrad cuts a deal to save the only family he has left. To rescue his sister from his uncle's clutches, Conrad must enter the Selection of the Twelve Trades.