A Darkening of Dragons - S. A. Patrick - Bog

"Three accidental heroes encounter one legendary villain in an epic dragon-filled adventure ... 13-year old piper Patch Brightwater is a boy in disgrace. Thrown in jail for playing a forbidden spell, he is no one's idea of a hero. But then he discovers a deadly truth--the evil Piper of Hamelyn is on the loose. With the help of Wren, a girl cursed to live as a rat, and Barver, a fire-breathing dracogriff, Patch must stop the Piper from sparking the biggest battle of them all"--