Edge Chronicles 7: The Last of the Sky Pirates (Penguin Random House Children's UK)

Rook Barkwater lives in the network of sewer-chambers beneath Undertown, the bustling main city of the Edgeworld. He dreams of becoming a librarian knight - one of those sent out to explore the mysteries of their world. Somewhere out there lie the secrets of the past - including the lost floating city of Sanctaphrax - and, maybe, hope for a future free from the fear of tyranny. When his chance comes, Rook grabs it! Breaking all the rules, he sets out on a journey to the Free Glades and beyond. His luck and determination lead him from one peril to another until, buried in the heart of the Deepwoods, Rook encounters a mysterious character - the last sky pirate - and is thrust into a bold adventure that dares to challenge the might of the dread Guardians of the Night.