Clockwork Angel by Cassandra Clare
Love is the most dangerous magic of all….
When Tessa Gray arrives in England during the reign of Queen Victoria, something terrifying is waiting for her in London’s Downworld, where vampires, warlocks and other supernatural folk stalk the gaslit streets. Friendless and hunted, Tessa seeks refuge with the Shadowhunter, a band of demon hunters. Drawn ever deeper into their world, she finds herself fascinated by - and torn between - two best friends.