Philip Reeve 
Scrivener’s Moon 

In a future land once known as Britain, nomad tribes are preparing to fight a terrifying enemy — the first-ever mobile city. Before London can launch itself, young engineer Fever Crumb must journey to the wastelands of the North. She seeks the ancient birthplace of the Scriven mutants. In the chaotic weeks before battle begins, Fever finds a mysterious black pyramid. The extraordinary secrets it contains will change her world forever. The seventh awe-inspiring adventure in the World of Mortal Engines series by a superb writer at the height of his powers.