Regardless of one's age, I think there are some novels that mostly anyone can relate to. Everyone has experiences which form who they are - be it high school, first loves, career moves, geographical repositioning. I think the most common relation among our culture is high school.
I read The Fault in Our Stars over Christmas break last year (before the film came out), and it made me fall in love with reading again. For a while, I would only read what was required of me in school. That is not to say I had lost interest in novels - on the contrary, I nearly prefer them over film or television. However, after years of reading textbooks and roughly uninteresting pieces of literature, I drew away from it. Reading just became more or less associated with work.
Then I read TFIOS. And I instantly became a Nerdfighter! Reading was fun again :)
Alas, I finally read Looking for Alaska. It was a perfect combination of teenage exploration and mystery. Not like Gone Girl mystery, but enough to keep the reader wondering what the countdown is leading to and what the aftermath will be.
So, thank you John Green! I can't wait to read Paper Towns next :)