Paper Town by John Green
Who is the real Margo?
Quentin Jacobsen has spent a lifetime loving the magnificent advernturous Margo Roth Spiegelman from afar. So when she opens his bedroom window late one night and summons him to join her on an ingenious campaign revenge - he follows.
After their all-night ends and a new day breaks, Q arrives at school to find that Margo has not. Always an enigma, she now becomes a mystery and Q soon learns that there are clues to be followed in his search for Margo.