Answer:
Hazel discovered that the author has published only one book, which she read and was incompletely left between. And, after the book came out, the author vanished and settled somewhere in Netherlands.
Hazel wanted him to respond to his letters because she can't wait forever to receive answers of her questions.
Step-by-step explanation:
'The Fault in Our Stars' is a novel written by John Green. The novel is about a sixteen-year-old Hazel Grace, who is suffering from cancer and Augustus Gus, a seventeen-year-old lover boy of the novel, who has tumor in leg.
In Chapter 4, after Hazel completed reading a novel titled 'An Imperiaal Affliction', she did some research on the author. The book was written by an author named Peter Van Houten, who published only one book in his life, which is 'An Imperial Affliction' and after the book came out, he vanished from the US and went on to live in Netherlands.
The book that he published was left incomplete and midsentenced, curious what happened afterwards, Hazel wrote letters to the author asking about the rest of the story. She perceived that the narrator, Anna, in the story must have died that's why it is left midsentence. She was curious to know what happened to other characters in the story, and wrote letters to the author. She wanted him to reply to her letters because she wanted to know her answers, as she didn't have forever to wait for her answers.