For teen girls, I can recommend
- The "Uglies" series by Scott Westerfeld. (Uglies, Pretties, Specials, and Extras)
- The Gemma Doyle Trilogy by Libba Bray (A Great and Terrible Beauty, Rebel Angels, and The Sweet Far Thing)
- A Modern Tale of Faerie by Holly Black (Valiant, Tithe, and Ironside)
- Safe-Keepers by Sharon Shinn (The Safe-Keeper's Secret, The Truth-Teller's Tale, and Dream-Maker's Magic
I would not recommend the Sookie Stackhouse/Southern Vampire series for teens -- much too much sex for my taste.