V. E Schwab

Making a Faustian bargain to live forever but never be remembered, a woman from early eighteenth-century France endures unacknowledged centuries before meeting a man who remembers her name.

Kell is one of the last Travelers-magicians with a rare, coveted ability to travel between parallel universes-as such, he can choose where he lands. There's Grey London, dirty and boring, without any magic, ruled by a mad King George. Then there's Red London, where life and magic are revered, and the Maresh Dynasty presides over a flourishing empire. There's White London, ruled by whoever has murdered their way to the throne. And once upon a time,...

Four months have passed since the shadow stone fell into Kell's possession. Four months since his path crossed with Delilah Bard. Four months since Rhy was wounded and the Dane twins fell, and the stone was cast with Holland's dying body through the rift, and into Black London.
In many ways, things have almost returned to normal, though Rhy is more sober, and Kell is now plagued by his guilt. Restless, and having given up smuggling, Kell is

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Ever since her near-fatal drowning, Cassidy has been able to pull back the "Veil" that separates the living from the dead and see ghosts, not that she wants to, and she was really looking forward to a ghost-free summer at the beach; however her parents are going to start filming a TV series about the world's most haunted places, starting with Edinburgh with its graveyards, castles, and restless phantoms--and Cass and her personal ghost companion,...