In John Green’s ‘Turtles All the Way Down,’ a teenager’s mind is at war with itself

Few subjects are more upsetting than young people with cancer. But John Green’s latest book, “Turtles All the Way Down” is somehow far darker, not so much because of the subject matter — though that’s dark, too – but because of how he chooses to write about it. This novel is by far his most difficult to read. It’s also his most astonishing.

At the heart of “Turtles All the Way Down” is Aza Holmes, 16, who suffers from terrible anxiety and obsessive-compulsive disorder. Her case sits on the icier, distant end of the spectrum. It is not easily managed.

People tend to associate OCD with repetitive behaviors, and that’s partly true in Aza’s case: She has a wound on her finger, self-inflicted, that she continually reopens in order to drain and re-sanitize.

But repetitive, intrusive thoughts are her true torment. She’s obsessed with, and repulsed by, the ecosystem of bacteria that seethes inside her, and the bacteria that live without. She can’t stop worrying about the rumble in her gut, or the possibility of contracting an infection, or the prospect of sweating, or not being able to stop sweating, or touching someone who is sweating. She has to fight off the urge to put hand sanitizer in her mouth. Sometimes the urge wins.

We spend long stretches inside Aza’s head, listening to these unsteady thoughts. The rational part of her, the one that sees a therapist and fitfully takes medication, tries to talk herself down. But her mind is in the throes of a civil war.

“Please let me go,” Aza tells her unwanted thoughts at a helpless moment. “I’ll do anything. I’ll stand down.”

If Green, the author of “The Fault in Our Stars,” were writing in his usual register, he’d interrupt Aza’s descents into these cognitive spirals — or “light-swallowing wormholes,” as she calls them — with a bit of humor. But he seems to have made a decision: If Aza can’t find relief, neither can we.

The first few chapters of “Turtles All the Way Down” are a little crude, a little awkward and a little slow. The premise: An Indianapolis billionaire has skipped town just before the police come to get him for bribery and fraud. A $100,000 reward is on offer to anyone who’s got the skinny on his whereabouts. Aza’s best friend, Daisy, remembers that Aza knows this guy’s son. Wouldn’t he know something? And wouldn’t a hundred grand be grand?

Aza does know his son. She’d met him years ago at “Sad Camp,” a summer program for kids who’d lost one or both of their parents. Aza had lost her father; Davis, the billionaire’s son, lost his mother. Now it seems that both his parents are gone.

So Aza reluctantly pays Davis a visit, and the novel begins in earnest. The two feel an ancient kinship, a bonding of broken souls. He’s terrified that his identity is inseparable from his money; she’s terrified that her identity is inseparable from her thoughts. “If you can’t pick what you do or think about,” she explains to him, “then maybe you aren’t really real, you know?”

A conventional love story begins. But it hits a bittersweet, unconventional dead end. Aza can’t kiss Davis without panicking. All those microbes.

Still, they bond. And Aza and Daisy try to solve the mystery of Davis’ father’s disappearance. At one point, Daisy gives Aza hell — doesn’t she see how her mental illness has made her self-absorbed? — and it’s awful. Then it isn’t. The friendships in Green’s novels are stirring and powerful.

“You are my favorite person,” Daisy tells Aza after they’ve reconciled. “I want to be buried next to you. We’ll have a shared tombstone.”

But the real question is: How does such a story end for Aza?

If an author has integrity, it should end plausibly. Green has integrity.

Still, I wasn’t prepared for the ending. It’s so surprising and moving and true that I became unstrung, incapable of reading it to my husband without breaking down. One needn’t be suffering like Aza to identify with it. One need only be human. Everyone, at some point, knows what it’s like when the mind develops a mind of its own.

Book review

‘Turtles All the Way Down’ by John Green, 286 pages, Dutton, $19.99.