Hazel is a girl who has lung cancer. She is home-schooled and doesn't like to leave her house. Her mom decides to make her go to a support group so she can meet other people and make some friends. When she is there she meets Augustus.
Augustus invited Hazel to watch a movie at his house. They end up talking about books and Hazel suggests her favorite book, "An Imperial Affliction". After Augustus reads it, he asks her tons of questions about the cliff-hanger ending that Hazel doesn't have answers for. Augustus and Hazel end up emailing the author about the book.
Hazel and Augustus get a reply back from the author, but it doesn't tell them the ending. Instead it tells them to fly out to Amsterdam to meet the author so he can tell them in person. Since they aren't able to fly out there with there own money, Augustus uses his wish that he gets granted from the cancer center.
When Hazel and Augustus get there, They find out that the author is a very rude person who drinks to much alcohol. The trip became worse when Augustus had to tell Hazel that he has cancer again and that he doesn't have long to live.
Soon, Augustus and Hazel go back home. Over a course of a few weeks, Augustus became extremely sick and passed away. Hazel was very upset and stayed in her room for a few days. At the funeral, the author of her favorite book showed up. He said that Augustus sent him a letter before he died saying to go to the funeral. He had something for Hazel but Hazel didn't take it.
A few days after the funeral, Hazel was talking to one of Augustus's friends. He said that Augustus wrote a letter to Hazel that he gave to the author. Hazel emailed the author's old assistant to see if she could go and get the letter for her. A few days later, Hazel gets an email. It has the letter from Augustus and the ending to her favorite book.