Turtles All the Way Down by John Green is a story about a high schooler named Aza who suffers from anxiety and obsessive-compulsive disorder. Aza is constantly fixated on germs to the point of occasionally drinking hand sanitizer. Even though she sees a therapist, she is not sure she'll ever get better and worries she will continue to be victimized by her obsessive thoughts.
Aza has Davis and Daisy with her throughout the novel. Davis, her love interest, is kind and understanding of Aza. He is dealing with his own problems as well; his father is a prominent businessman being accused of fraud and has gone missing. Daisy is Aza's best friend and, despite being pretty extroverted and at times overwhelming to Aza, fiercely supports her.
The novel weaves through Aza's struggles with her mental illness and the mystery of Davis and his father, a mystery Daisy is determined to unravel. Aza and Daisy do find several clues to solve the mystery, but some readers have found the conclusion to the novel unsatisfying. There is no indication that Aza will escape her obsessive thoughts anytime soon, and Davis, after writing a final post on his blog, does not contact Aza again. However, Aza does get somewhat better. She and Daisy start clubs at school in order to put extracurriculars on their college applications, and the two hang out together on most nights. Even though it seems Aza and Davis will not end up together, Green writes with a tone of hope that Aza will continue to slowly improve.