It’s been six years since American author John Green struck gold with his phenomenally successful “sick-lit”, The Fault in Our Stars, for young adults. In an announcement made on the television show Good Morning America on Thursday, it was revealed that 39-year-old Green’s new book, titled Turtles All The Way Down, will be released on October 10 this year.

The book cover, in his trademark minimalistic style, with handwriting-like font taking up most of the space in black and an orange spiral in the background, leaves much to the imagination. Since the cover doesn’t give much away – other than the interpretation that the downward spiral represents a mental illness that features in the book – there is much speculation over the title, and what exactly turtles have to do with the story.

Apparently not much, as “Turtles all the way down” is a “philosophical joke that says the world is flat and we’re all just on a giant turtle,” reported Good Morning America.

Here’s the lowdown on the book from the author’s website:

“Sixteen-year-old Aza never intended to pursue the mystery of fugitive billionaire Russell Pickett, but there’s a hundred-thousand-dollar reward at stake and her Best and Most Fearless Friend, Daisy, is eager to investigate. So together, they navigate the short distance and broad divides that separate them from Russell Pickett’s son, Davis. Aza is trying. She is trying to be a good daughter, a good friend, a good student, and maybe even a good detective, while also living within the ever-tightening spiral of her own thoughts.”

The book is reportedly very personal for Green as for the first time he has written about a mental illness that has affected him since childhood. The Fault in Our Stars, which was adapted to a hugely successful film in 2014, also features a 16-year-old girl, Hazel Grace Lancaster. Cancer plays a central role and the book features her doomed love story with another patient.