The Fault in Our Stars
by John Green
We've got your back. With the Tough-O-Meter, you'll know whether to bring extra layers or Swiss army knives as you summit the literary mountain. (10 = Toughest)
(5) Tree Line
This one's a little tougher to summit. Not only is the book written with some slightly elevated vocabulary, the themes—cancer, death, teenage sex—are also more appropriate for a more mature audience. But climb on up! The weather's fine up here.