Scrivener's Moon (Mortal Engines Prequel 2)

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 journeys to the wastelands of the North to seek out 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.