Worldshaker by Richard Harland

A sound brought Col out of a deep sleep. Something was happening out in the corridor. Urgent footsteps, orders and questions, the clangs of many doors opening and closing. Cabin by cabin, the disturbance came closer. His own cabin remained in darkness – until suddenly the door was flung open.

Colbert Porpetine is the grandson and heir apparent of the Supreme Commander of Worldshaker, an enormous juggernaut city that can travel across land and water. Col has been well brought up, and is aware of his important position, and the responsibilties it entails. So when a runaway Filthy from below turns up in his bedroom, his first instinct is to call for help and have the disgusting thing arrested. But he doesn't. The Filthy girl doesn't seem sub-human. She can speak as well as he can, and she wants to learn to read... It doesn't match what he's been told about the Filthies, and before he knows it, Col finds himself in a dark secret world of rust, rivets and rebellion.

Worldshaker is longlisted for the Gold Inky