Quentin Jacobsen has spent a lifetime loving the magnificently adventurous Margo Roth Spiegelman from afar. So when she cracks open a window and climbs back into his life–dressed like a ninja and summoning him for an ingenious campaign of revenge–he follows. After their all-nighter ends and a new day breaks, Q arrives at school to discover that Margo, always an enigma, has now become a mystery. But Q soon learns that there are clues–and they’re for him. Urged down a disconnected path, the closer he gets, the less Q sees of the girl he thought he knew.
Paper Towns (by John Green) is really one of the best books that I've ever read. This one falls in the category of teen adventure/drama, with a backstory of romance. The characters are seniors in high school.