City of Lost Souls (The Mortal Instruments #5) by Cassandra Clare

Synopsis What price is too high to pay, even for love? When Jace and Clary meet again, Clary is horrified to discover that the Lilith’s magic has bound Jace together with her evil brother Sebastian, and that Jace has become a servant of evil. The Clave is out to destroy Sebastian, but there is no…