5 Things We Know About John Green's Turtles All the Way Down, His First Book in 5 Years

John Green hasn't released a new novel since 2012's The Fault in Our Stars, but that's all about to change. The bestselling author — who also wrote YA novels Looking For Alaska and Paper Towns — has a new book in the works, titled Turtles All the Way Down. Green's return has been highly anticipated, and after announcing the news of his new book on Twitter and during his VidCon appearance in late June, a few choice details about it have started to trickle out (including the meaning behind that mysterious title and the release date!). Here's what we know so far.

On his website, Green lays out the basics for the upcoming novel. It will follow 16-year-old Aza, who's struggling "to be a good daughter, a good friend, and a good student" all while also trying to solve one of the greatest mysteries of her time. With the help of "her Best and Most Fearless Friend Daisy," Aza sets out to uncover what happened to fugitive billionaire Russell Pickett (and possibly collect a $100,000 reward in the process). Aza and Daisy's journey to Russell Pickett's son, Davis, will be an emotional and illuminating one, as Aza also attempts to deal with her own mental illness.

During Green's Ask Me Anything session on Reddit in 2015, the 39-year-old author opened up about his experience with obsessive compulsive disorder and anxiety. "I've known that I have this mental illness for a long time, and I've had a lot of therapy and learned a lot of strategies for dealing with my illness," he wrote. "I know the benefits of exercise and meditation and medication and CBT strategies and etc."

In a statement from publisher Dutton Books, an imprint of Penguin Young Readers, Green revealed that Turtles All the Way Down was written as a way for him to work through his own struggles with mental illness. "This is my first attempt to write directly about the kind of mental illness that has affected my life since childhood, so while the story is fictional, it is also quite personal," he said.

"Turtles all the way down" is actually a popular expression in cosmology that comes from an anecdote explaining "the unmoved mover" paradox. It posits that Earth is actually flat and is riding on the back of "a World Turtle," which itself is on the back of another turtle, and so on. The end of the anecdote concludes that it's "turtles all the way down." Apparently Aza will be a fan of The Big Bang Theory.

It's set to hit bookshelves on Oct. 10.