NASHVILLE, Tenn. (AP) — In the years since John Green's tear-jerker love story about two teen cancer patients became a best-seller in 2012, the young adult novelist and video blogger wondered if he would ever be able to write another book. After "The Fault in Our Stars" sold over 45 million copies and was adapted into a popular film, the pressure was immense.

"I definitely felt like people were looking over my shoulder while I was trying to write," Green said during a recent book tour stop in Nashville, Tennessee. "I think that was the biggest reason why it took me so many years between books was because I definitely felt overwhelmed by the scale of things."

But to the relief of his many passionate fans, Green is back with his new novel, "Turtles All the Way Down," released this month. Green found inspiration in a mental disorder he lives with but has long struggled to describe in his writing.

His female protagonist in "Turtles" is obsessive-compulsive, like Green himself. She's thrust into the role of a teen detective trying to locate a missing billionaire while falling for his son. But unlike Sherlock Homes, 16-year-old Aza Holmes can barely see the world outside her own head as her illness takes her on ever-deepening spirals of repeated thoughts about anxieties and identity.

"That is my experience of OCD," Green said. "It does not come with secret detective powers despite the convention of the Sherlock Holmes stories. My experience with OCD is that it makes me incredibly unobservant."

Aza's disorder manifests itself as a fear of bacterial infection. When she pushes back against these intrusive thoughts, the anxiety increases until she feels no longer in control of her own body or actions. She constantly opens a wound on her finger to disinfect herself, which escalates even further in the climax of the novel.

Although Green has been dealing with OCD since childhood, he avoided writing it into his stories because he was afraid of how it would affect him.

"I think partly because I felt like writing about it would give it power somehow, when in fact it didn't," Green said.

But he also struggled with how to describe the psychological torment of not feeling in control of yourself and losing your own identity in a mental illness.

"It's really difficult to give it form or find language for it," Green said. "That was one of the things I wanted to write about was how much language struggles in the face of pain."

The characters in his new book find different ways and technologies to communicate with each other — through blogs, poems, texting, or "Star Wars" fan fiction — to make up for their fears of interaction in real life.

For a decade, Green and his brother, Hank, a musician and author, have been interacting with their fans via their YouTube collaboration called the Vlogbrothers. Along the way, they've built a loyal online community of fans who identify as "nerdfighters" and follow the motto of "Don't Forget To Be Awesome." Green joked that he could connect with fans "while never leaving my basement, which is very appealing."

"I love being a part of that community and it's tremendously invigorating to me to see their fan art, to read their comments and read fan fiction about my books," Green said.

By now his audience has grown far outside young adult readers, but he said that hasn't really changed his approach to writing about teens.

"I think the emotional experiences of being a teenager are pretty universal," Green said. "And I think the questions that they are asking — about identity and how you acknowledge personhood in other people and whether meaning in life is constructed by us or derived by something else — those are questions that are still fairly important to me."

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Online:

www.johngreenbooks.com

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Follow Kristin M. Hall at Twitter.com/kmhall