Maybe you've Cassandra Clare's series, The Mortal Instruments. Or maybe you've read The Infernal Devices books. She's a fantastic writer and her fantasy worlds are full of depth and lore. Holly Black is another name you should know. She writes dark stuff, like The Coldest Girl in Coldtown.
Together, they've been writing a new, five book series called Magisterium.
After watching this interview, I knew I had to read book one.