Yowza. We told you The Fault in Our Stars would tackle some pretty heady themes, so here's one for the books. Hazel and Augustus are pretty cerebral kids, and they're constantly going over philosophical ideas about their existence and what place they hold in the world. They feel the need to figure things out, maybe because they're acutely aware that they don't have an endless amount of time left. They are trying to read, learn, and drink up all of life's lessons at once—which leads to some pretty epic adventures over the course of the story.
Hazel's obsession with the ending of An Imperial Affliction has a whole lot to do with her desire to figure out how life works.
Because of their cancer, Augustus and Hazel spend a lot more time thinking about their mortality than typical teenagers.