By Philip Reeve This is a steam punk industrial revolution sci-fi fantasy story set in a time when the major cities of the world are individual self-contained entities that travel across the barren earth. This is a world eat world time and bigger, stronger cities chase after smaller, weaker cities and towns and devour them, keeping scrap that might be useful and discarding the rest. There is your usual scavenger crew, those out to make a quick buck off the misfortune of others who scavenge the discards of cities devoured. There is also the typical class systems of upper and lower with the power hungry upper class leaders readily betraying each other to further their own interests – who can really be trusted in this world? Tom is a 3rd class apprentice historian living in the traction city of London in this world. He has been sent to work in the gut of London, which is the bottom station that is currently dealing with the recent acquisition of a small town and needs to filter the material to decide what to keep and what to get rid of. While there, Tom saves his mentor from a seemingly deranged assassin, but then suddenly finds himself outside of London in the mud pit with Hester, the would be killer. Weighing his options, Tom decides to follow Hester and their adventures begin as they both try to get back to London, which by now has moved away from them at a rapid pace. Hester and Tom join forces to uncover the truth about what is really happening on London and meet a wide array of friends and foe along the way to the final battle. For sci-fi fans who love a detailed story with mini battles, setbacks and triumphs, this is a must read. this is the first in the four book Mortal Engines series.