The Book of Dead Days by Marcus Sedgwick

Two children, Boy, nameless servant and Willow, assistant to singer Madame Beauchance. A magician and alchemist named Valerian using Boy and infernal powers to create illusions for his act at the Great Theatre.

It is the Dead Days, those oddly quiet days between Christmas and New Year. And a terrible drama plays out in the City, a great sprawling decaying metropolis gripped in winter, once magnificent and powerful, now rotting and impoverished.

Valerian was always unpredicatable, carrying out his mysterious experiments in the rambling ruin of the Yellow House. But now he is becoming increasingly volatile as New Year and his deadline for an infernal pact runs out. Boy and Willow are drawn into a breakneck adventure trying to find a mysterious book that will let the slippery Valerian once more cheat his fate but at a terrible price.

Sedgwick's writing is fast paced but also evocative and haunting, you feel the cold of the City seep into your bones as you're borne away on his adventure.

Communion Town: A City in Ten Chapters by Sam Thompson

A hallucinogenic book.  Thompson presents us with 10 chapters, each a different character describing their experiences in a city almost like any other great city: of slums, murders, subway stations, warren-like alleys and bright public façades.  The Flâneur of Glory Port - a Jack-the-Ripper type bogeyman - and deformed mutants haunt the shadows in many of the stories.  The narrators vary in widely in social position and the stories in timbre.  A hard-boiled detective speaks as if channelling Sam Spade, another Sherlock Holmes.  Slaughtermen, immigrants, reclusives, automatons, all speak and reveal a different city, one that is just slightly futuristic, tangible, chilling and mesmerising.