I also would suggest the Gemma Doyle Trilogy by Libba Bray. It really was wonderful and was something a little bit different. Obviously, the Twilight Saga would be another good one. I am starting a series that my mom recommended to me (we both get a kick out of YA): The House of Night books by PC Cast. They're about vampires, and I see a few others have recommended them! Good luck!
P.S. I work at a library and the Clique series by Harrison seems to be very popular with that age group!