A darkling plain - Philip Reeve

Wren and her father Tom Natsworthy travel the Bird
Roads in their airship, trying to forget Hester's betrayal. But
in the ruined wreckage of the city of London they make a discovery
that changes everything. And Hester faces an implacable foe with
the means and the will to destroy the entire human race.

MORTAL ENGINES launched Philip Reeve's brilliantly-imagined creation,
the world of the Traction Era, where mobile cities fight for
survival in a post-apocalyptic future. Now, in time for the film
debut, the critically acclaimed MORTAL ENGINES quartet is repackaged
with a fantastic and eye-catching cover featuring new artwork.