Clockwork Angel Book by Cassandra Clare

When Tessa Gray crosses the ocean to find her brother, her destination is England, the time is the reign of Queen Victoria, and something terrifying is waiting for her in London’s Downworld, where vampires, warlocks, and other supernatural folk stalk the gaslit streets. Only the Shadowhunters, warriors dedicated to ridding the world of demons, keep order amidst the chaos.
Kidnapped by a secret organization called The Pandemonium Club, Tessa learns that she herself is a Downworlder with a rare ability: the power to transform into another person. What’s more, the Magister, the shadowy figure who runs the Club, will stop at nothing to claim Tessa’s power for his own.