“I wanted a really different kind of challenge,” says Kristin Cashore, about writing her most recent book. “My brain needed a new kind of puzzle.” For Cashore, whose Graceling Realm series has sold more than 1.5 million copies and been translated into 33 languages, that meant writing her first standalone novel, Jane, Unlimited (Penguin/Dawson, Sept.). “It’s still fantasy in the sense that impossible things happen, but not a high-quest fantasy,” she explains. “It’s full of umbrellas and adventure and a big, weird, mysterious house. It’s a little bit of an homage to du Maurier’s Rebecca, and other ‘orphan visits a house of mystery’ books. Mostly, I’m hoping it’s a puzzle, but a puzzle that’s full of heart.”

Cashore got the idea for the novel driving to a Christmas party with her sister. “I had this thought: ‘What if I were to do something like the Choose Your Own Adventure books I read growing up? What if I wrote someone’s adventure, and they had choices that each led to a story line in a different genre?’ ” Those genres, Cashore reveals, are “mystery, spy, horror, sci-fi, and fantasy, all tied together.” It was, she admits, “really challenging figuring out how to get all that on the page.”

After Bitterblue, the last book in her Graceling Realm series, was published in 2012, Cashore decided she needed a break from fantasies. “Writing it was an emotionally exhausting journey, and it also felt like the book was the natural end of that cycle. I realized that all along Jane, Unlimited was what I had been writing toward.” Cashore’s hope for her new novel is that “readers will care about Jane, and the book will give them a feeling of magic and possibility.”

The author has been writing full-time over the past five years. When not writing, Cashore has embarked on a few adventures of her own: “Every month over the past year, my partner and I have done something neither of us had ever done before, like indoor skydiving or building a gingerbread house.” In April, Cashore moved into her first office outside of her home. “It’s really changed the way I work,” she says. “I have fewer distractions available—like convincing myself it would be better to clean the floors instead of writing—so I’m more focused.” She still handwrites her novels in a ruled notebook, using a needle-point pen with blue ink, but, she adds, “Once I have enough written that I begin to worry about what would happen if the house burned down, I use voice recognition software to put it on the computer.”

Today, 2–3 p.m. Kristin Cashore will sign galleys of Jane, Unlimited in the Penguin Random House booth (1921).