I'm not sure how to approach a critical review for a book like this.
There are two teenagers dealing with cancer and their own mortality here. I don't really recognize them as real teenagers in the way they speak or in how clever they are with words. But they are honest with the world, each other, and themselves, and that is commendable.
The book is heartwrenching. But it is hopeful at the end. I think probably the best thing I can say about it is simply this: I hate being emotionally manipulated by an author. John Green didn't do that at all. He just told a story worth telling.