In this fantasy novel, we follow the story of a rare magician with the ability to travel between parallel Londons—Red, Grey, White, and, once upon a time, Black. Each London has a different level of magic, and the balance of power is precarious. The protagonist serves as a messenger and smuggler between the Londons, adhering to a strict set of rules to keep these worlds separate. However, when an unexpected encounter leads to the discovery of a dangerous artifact from the forbidden Black London, the magician must navigate treacherous political waters and dark magic, with the help of an adventurous thief, to prevent catastrophic destruction.

The 10507th greatest book of all time