Turtles all the way down - John Green

Sixteen-year-old Aza is trying to be a good daughter, a good friend, and a good student. She’s also trying to track down fugitive billionaire Russell Pickett, who has vanished without a trace. Alongside her Best and Most Fearless Friend, Daisy, Aza sets off in pursuit of the truth—and a $100,000 reward.

The trail leads them to Pickett’s son, Davis, a sometime friend of Aza’s who might have the clues they need. But as her compulsive thought spirals take an ever-tighter grip on her mind, Aza finds herself struggling to keep her investigations—and her life—from falling apart.