"A Darker Shade of Magic" is a fantasy novel by V.E. Schwab, set in a universe with parallel Londons: Red London, Grey London, White London, and Black London. Each London has varying levels of magic, with Red London being the most vibrant and Black London having succumbed to its dangers. The story follows Kell, a magician who can travel between these worlds, and Lila Bard, a cunning thief from Grey London. As Kell navigates the political tensions and magical threats between the Londons, he becomes embroiled in a dangerous adventure. The novel explores themes of identity, power, and the consequences of magic, as Kell and Lila confront dark forces that threaten their worlds.