This book is absolutely fantastic. 
 This book is about a magician named Kell who has the rare ability to move between parallel Londons. There is Grey London, Red London {from which Kell is from}, White London and Black London. Kells job is it to bring messages from the royalty of one London to the other, but while he does that, he also smuggles some bits and pieces for fun, which is - of course - forbidden. And one day Kell smuggles something, he really shouldn't have, something dark and dangerous. This book is also about a thief -Delilah Bart - short Lila - from Grey London {or dull London - it's how she would call it} who wants nothing more than to finally find an adventure. And oh boy does she find one when she finally meets Kell.... 
 It's hard to describe the plot line of this book but it is absolutely fantastic, the characters are amazingly written as well as the world building. It's fantasy, magic and a big adventure with darkness in it I wasn't prepared for...