The Infernal Devices is a young adult series written by Cassandra Clare, who resides in America. It is set in the 19th Century, in London. The main protagonist is Tessa Gray who has traveled from America, to London. The series follows her as she is introduced to Shadowhunter world. Shadowhunters are half angel, half human. They face demons, warlocks, fey and vampires throughout the books.
There are three published books in the series, which is now completed after the release of Clockwork Princess in March, 2013.
You can find Cassandra Clare’s website here: http://www.cassandraclare.com/
Her twitter is: @cassieclare