What is the analysis of The Fault in Our Stars?

The Fault in Our Stars is John Green's sixth novel. The novel tells the story of Hazel Grace Lancaster, a terminally ill teenager who has thyroid cancer. Hazel is consistently struggling with an existential crisis that has resulted from her childhood illness. She is generally pessimistic and sarcastic, leading her mom to prompt her to attend a cancer support group. Hazel is against the idea at first, but that is where she meets Augustus Waters—her future boyfriend.
Hazel and Augustus eventually fall in love, and much of the plot revolves around their quest to meet the author of Hazel’s favorite novel, Peter Van Houten. The book An Imperial Affliction ends without a conclusion or closure, but according to Hazel, it is the most realistic treatment of cancer she has seen in a novel. The pair eventually go to Amsterdam to talk about the book with Van Houten, but he ends up being a terrible drunk. Hazel and Augustus spend the time together instead, and Hazel realizes she loves Gus.
Hazel is still dealing with her cancer in the novel, and as a result, she considers herself “a grenade”—something that will eventually explode and hurt those who love her. When Augustus reveals that his cancer, supposedly taken care of when his leg was amputated, has returned and spread, Hazel realizes that he is the grenade. Hazel has to live with Gus and deal with his death up close. After his funeral, she reads the obituary that he wrote for her and affirms to herself that she is happy with the choices she has made.
Ultimately, The Fault in Our Stars deals with the idea of choice. In the face of non-choice, death by cancer, the book focuses on the ability of people to make choices in the face of oblivion and death. Augustus touches on this concept in his letter to Van Houten about Hazel’s obituary:

You don’t get to choose if you get hurt in this world, old man, but you do have some say in who hurts you. I like my choices. I hope she likes hers. (Chapter 25)

Hazel realizes that she does like her choice and that it is something that she is going to live with, because her love for Augustus is worth the eventual pain she will feel from his death. The novel is saying that love, a choice we make, is ultimately worth the pain and suffering we experience from dealing with death and oblivion. That sentiment is similar to what Augustus first expresses in Chapter 10 of the novel:

I'm in love with you, and I know that love is just a shout into the void, and that oblivion is inevitable, and that we're all doomed and that there will come a day when all our labor has been returned to dust, and I know the sun will swallow the only earth we'll ever have, and I am in love with you.

The final statement of the novel that goes along with Augustus confessing his love, despite the hurt that might happen, is that even in the face of death, we keep on living while we can. While the characters in the book are facing a tangible death, everyone ultimately faces death existentially, and we make choices to live and love, despite what might eventually happen to us. At the end of the novel, Hazel is still alive, and despite the hurt and the “scar” that Augustus left, she is happy with the choice she made to love Augustus.