John Greene's books, including The Fault in Our Stars, was based off real events and characteristics from his own life. In The Fault in Our Stars, Hazel, the main character, has cancer. The idea of making Hazel have cancer came from John Greene's own life where he used to work in a hospital. John was always surrounded by ill patients which inspired him to write a story. Another characteristic of Hazels is that she is interested in science, literature, and history. These are all subjects that John Greene taught when he was a professor. John Greene is interested in health and science and even created his own YouTube channel. All of these interests that John Greene has and all of the events from his life were incorporated into his novels.