A Darker Shade of Magic (2015)

In a universe with parallel Londons—Red, Grey, White, and Black—Kell is one of the last Antari, a magician with the ability to travel between the worlds. He serves the monarchy of Red London but is also a smuggler. When he encounters Delilah Bard, a cunning thief from Grey London, their journey leads them into danger and intrigue as they confront dark magic and power struggles.