A Darkness of Dragons — S.A. Patrick

Waterstones Children's Book of the Month for November 2018
Ten years on after the dreaded Piper of Hamelyn incident, young Piper Patch Brightwater finds himself on the run from a prison sentence for innocently playing a forbidden spell.
Accompanied by Wren, a girl cursed to live as a rat, and Barver, the fire-breathing dracogriff, the fleeing Patch suddenly finds himself pitched against the malevolence of the Piper himself.
Expect high-octane adventure as S.A. Patrick's children’s debut assembles a truly inspired fantasy world of dragons, magic and the sheer power of music, perfect for fans of the younger Terry Pratchett series.