Fever Crumb, By Philip Reeve

Philip Reeve's intricate imagination makes J K Rowling feel like Enid Blyton, but he is as adept as she is at creating likeable characters, subtle villains and situations where good is hard to sort from evil.

Fever Crumb takes place after an apocalyptic end to civilisation. The North Sea is a desert and wheeled land-ships trundle around Europe. All trade centres around archaeology, as the survivors of Armageddon try to understand the purpose of the mangled remains of our machines, and a markedly medieval civic framework operates.

Reeve's first book, Mortal Engines, started a thousand years later. London, "a moving mountain of metal", roamed on gigantic caterpillar tracks north to the Ice Waste and south to the Mediterranean in search of smaller cities. This was "Municipal Darwinism", in which nomadic cities preyed on slower-moving towns which in turn preyed on static settlements. The world had worked like this "ever since the great engineer Nicolas Quirke had turned London into the first Traction City". The adventures of Reeve's characters continued in Predator's Gold and Infernal Devices, and climaxed in A Darkling Plain.

Now Reeve has cast back into the past. Fever Crumb is a foundling who has lived with the utterly rational Guild of Engineers in Godshawks's Head, a towering iron folly made by Auric Godshawk, the last of London's Scriven overlords. Rebellious Londoners long ago destroyed the brilliant, but autocratic Scrivens, but now are under threat from Northern nomads who have made more practical use of the world's lost technology. Fever can save London, for her brain holds the key to Godshawk's genius. But will she risk losing herself in the process of discovery?

Reeve's vividly pictorial writing is becoming ever more accomplished and fluent. I enjoyed his plays on London place names (Pickled Eel Circus, Hampster's Heath) and shuddered at the sinister robot paperboys. There is always method in his madness: this is a book about establishing identity, being true to yourself, and keeping children, the only hopes of the future, safe.