The Infernal Devices is a trilogy that follows the shadowhunter world as well as the Mortal Instruments, they both are by Cassandra Clare.
Tessa Gray only wishes to see her brother, the last of her family in London, so you can see how her being kidnapped upon arrival, upset those plans. Her kidnappers, the Dark sisters, force her to inflict pain on herself as she discovers that she has a magical power. She can literally change into someone else and access their thoughts, and it wouldn't have been too bad, if she hadn't learned that it was all so that they could hand her over to the Magister for marriage.
As Tessa tries to run away, she runs into handsome Will Herondale. Will has been tracking a trail of murders and missing items for weeks now, and they lend him to the Dark sisters' house. Lucky for Tessa that Will was there because he is shadowhunter, bound to protect. Will then brings Tessa to the London Institute, where he and other shadowhunters live. There she learns about a world hidden within her own, but Tessa