Shades of Magic Trilogy by V. E. Schwab

Description

Kell is one of the last Antari–magicians with a rare, coveted ability to travel between parallel Londons: Red, Grey, White, and, once upon a time, Black. Officially, he’s an ambassador; unofficially, he’s a smuggler. After an exchange goes awry, Kell escapes to Grey London and runs into Delilah Bard, a cut-purse with lofty aspirations. Now perilous magic is afoot, and treachery lurks at every turn. To save all of the worlds, they’ll first need to stay alive.