First, let me describe the basic plot. Quentin is a high school senior who is about to graduate. He's an average guy with a few average close guy friends who do average high school guy things like play video games and IM each other at night. He has a neighbor named Margo Roth Spiegelman whom he has known since he was a child. Like many childhood friends, they grew apart as they got older, even though they had a very intense childhood experience of finding a man dead in a park at the very beginning of the novel. Now, however, while Quentin is quite your average high schooler, Margo Roth Spiegelman is decidedly un-average and hangs out with the beautiful and popular people. She has a popular boyfriend. Then one night a couple weeks before graduation, she slips into Quentin's bedroom and convinces him to take his mom's minivan and drive her around creating mayhem, mostly related to retaliating against her friends for a recent wrong that was done to her, but also including some other adventures just for Quentin and/or Margo Roth Spiegelman's sake(s), such as breaking into Sea World. The following day, Quentin has the natural reaction of wondering how/if this night will change his relationship with Margo Roth Spiegelman. But . . . she disappears! This isn't all that unusual, though, since we find out from her parents that she has done this before. And when she has done this before, she has left obscure clues as to where she was going and expected her parents to figure them out and find her. They are tired of these games and don't even attempt to try to look for her. Quentin, on the other hand, is not only attracted to and worried about her (she has shown some serious signs of suicide/depression recently), but he finds a glaring clue on her window shade that leads him to another series of clues as to her whereabouts. He isn't sure if he's on the right track, let alone whether MRS is even alive or intended for him to follow the clues, but he pursues the potential clues anyway in the hopes of finding her alive.
So that is the plot. The novel reminded me of a quotation that I wrote down in college because it seemed so viscerally true to me (sorry I don't remember the source anymore). It's by Jane Mansbridge and Susan Moller Okin: "We construct ourselves in part through the narratives we create about our lives." I don't feel like I can really explain it in relation to Paper Towns too much without giving away the ending, but if I were (for some reason) writing a paper about it, I think that would be the basis of my thesis. If/when you read the novel, think of this quotation particularly when you read the metaphor discussion. The metaphors you choose are really important.
My favorite scene in the novel is when Quentin cleans out his locker at the end of the school year. I felt really moved by how true-to-life it seemed and how ambivalent that time of your life can be, as well as how something so mundane can be the kind of event that, while you may not expect it, ends up really affecting you in a significant way.
And while this doesn't really have anything to do with the poignancy I felt in that scene, can I tell you how fascinating lockers are at the end of the school year? I never thought about this as a student (one who dutifully cleaned out her locker each year when they told you to), but as a teacher, my eyes were opened to a whole fascinating world of post-school-year locker sociology. At the end of the school year, the custodians go around and open up all the lockers so they can come by and easily clean them out. This is fascinating. Students leave so much stuff in there! On the one hand, it is kind of sad because students will leave things like tons of perfectly good school supplies, some that may have never even been used or opened. I have often thought it is a huge waste and something that would be great for charity. On another hand, you have really interesting items like empty alcohol bottles. I'm sure I am/was just naive, but who brings the actual alcohol bottle to school and just leaves it in their locker?
(I also thought more than once as I read this book: John Green seems to like writing about average high school boys who have a thing for unconventional, independent high school girls who intrigue them.)