[Book] Mortal Engines by Philip Reeve
Book cover Over a thousand years before the book's present, there was a war that effectively destroyed all of society. Picking up the pieces of the technology that was left behind, London was put onto treads, run by steam, so that it find and consume other towns for resources and, ultimately, more fuel to keep moving. Over time, other towns and cities did the same, while another group, called the Anti-Traction League, created a defensive wall across the only pass in a mountain range to keep these traction cities at bay on the other side....