Paper Towns, by John Green
Q has known his neighbor Margo Roth Speigelman since they were both little kids. Once they were close friends but as high school comes to a close they move in completely different circles. Q hangs out with the band nerds and Margo Roth Speigelman (you always have to use her full name) is one of the coolest of cool kids. But one night, Margo Roth Speigelman knocks on Q's window, forcing their circles to intersect. After a night of righteous pranks designed by Margo Roth Speigelman to right some wrongs and punish wrong-doers, Q thinks maybe, just maybe, they can be friends again. But then Margo Roth Speigelman disappears. The longer Q looks for her, the more he discovers about who she really is and how the surface Margo Roth Speigelman is not the whole picture at all.

Although there are some very funny moments, this is not a primarily funny book. Those funny moments balance out discussions of philosophy and poetry, real angst about what has happened to Margo Roth Speigelman, and thoughts about the meaning of friendship.