John Green doesn't pull any punches with his material. Yes it's about a junior boy in boarding school, but the book is also full of philosophical musings (hello, last words of famous dead people, religious conversations, not to mention healthy doses of alcohol, cigarettes, and sex. The subject matter alone—teen drinking, death, grief, and suffering—bumps this book up to Tree Line.
Not only that, but John Green has never dumbed down language for teenagers. There's swearing, of course, because of the voice John Green writes with, but there's also a lot of challenging vocabulary. The book's slightly more difficult than your average young adult novel in both content and language, but it's definitely worth the struggle up the slope.