Caraval Author Stephanie Garber's New Novel Alchemy of Secrets Is a Supernatural Thriller — See the Cover! (Exclusive)

Stephanie Garber is back with a highly-anticipated new book.

PEOPLE has an exclusive first look at the cover of the bestselling author’s adult debut, Alchemy of Secrets. The novel is forthcoming from Flatiron Books this fall.

The new novel follows Holland St. James, a college student intrigued by a class about local myths. Holland is a firm believer in magic, especially after she tracks down a legend about the Watch Man, who predicts when people will die.

But when the Watch Man tells Holland that she’s set to die at midnight, she’s sent on a journey around Los Angeles to find the Alchemical Heart, an ancient object that will prevent her death. Along the way, Holland meets a mysterious stranger adamant on helping her — but the deeper the two get in their search, the more Holland understands that she can’t trust everybody.

Garber, known for the young adult fantasy series Caraval and Once Upon a Broken Heart, tells PEOPLE that Alchemy of Secrets allowed her to explore some of her own interests, especially while developing the novel's fictional college course Folklore 517: Local Legends and Urban Myths.

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“When I first started writing these legends, I got a little carried away and they became a huge inspiration for this story,” Garber says. “But Alchemy of Secrets was also inspired by so many of the things that I find fascinating — secret societies, old Hollywood, the paranormal, treasure hunts full of puzzles, dark academia and star-crossed lovers.”

As an avid thriller reader, Garber was also interested in creating a fast-paced story, à la Dan Brown’s The Da Vinci Code, with supernatural and romantic elements, in the vein of Deborah Harkness’ A Discovery of Witches. Stepping into the adult genre, however, did mean some changes.

“I think a big difference between Alchemy of Secrets and my YA novels is the world,” the author says. “This is my first novel set in our world, and one of my goals was to tell a story where readers would have a difficult time telling the difference between the mythology I created for this book, and mythology that I actually pulled from our world.”

And though Garber notes there will be Easter eggs in Alchemy of Secrets, the novel marks a new step forward too.

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“Since this is my first adult novel and my first novel set outside of the world of Cararval I really wanted to make sure that it was separate from that series and completely accessible to new readers,” Garber says.

Alchemy of Secrets will be published on Oct. 7 and is now available for preorder, wherever books are sold.