On a long drive from her home near Chicago to Carleton College in Minnesota—which she attended as a freshman before transferring to Northwestern—Veronica Roth saw on a billboard an image of a person leaping off a building.

"I wondered why someone would do that," she recalls. "At the time, I was also taking Intro to Psych and we were studying the treatment of phobias by repeated exposure to fears."

From those musings came the underlying concept of Divergent (HarperCollins/ Tegen), Roth's thought-provoking debut set in a crumbling dystopian Chicago, where citizens are divided into five factions depending on their beliefs, passions, and loyalties. When the main character, Beatrice Prior, or "Tris," forsakes her Abnegation family to become a Dauntless, she must confront her deepest fears, guard an ominous secret, and, incidentally, leap off a few buildings.

Roth began writing around the time she got too old to play pretend in the backyard. After reading the entire Animorphs series and Ender's Game a number of times, she knew exactly what genre she was headed for, and what age group. "I never had the same enthusiasm for an adult book that I do for young adult literature," she explains. "I have a deep respect and love for this genre and these readers."

Roth started writing Divergent while in college, originally from the perspective of Tobias, Tris's mentor and love interest. But Tobias's voice didn't feel quite right. So Roth switched to a strong-willed female narrator. "I knew that Tris would not be nearly as compelling if she was perfect," Roth says. "Her flaw became her lack of compassion."

Which sometimes made Tris a difficult protagonist to like. But Roth believes that having your character make unpopular choices is a "weird sacrifice that's always for the greater good. The stronger a character is, the more flawed she has to be."

While shopping around a different manuscript as she polished Divergent, Roth caught the eye of Joanna Stampfel-Volpe of Nancy Coffey Literary. Though Stampfel-Volpe turned down that first project, she loved Roth's writing and invited her to submit other manuscripts. After reading Divergent, Stampfel-Volpe quickly signed her on. An offer from HarperCollins came only four days after Divergent went out on submission.

Roth says working with editor Molly O'Neill has been a match made in heaven: "We have these direct message conversations on Twitter. Molly will send me a link and we'll tweet about how it relates to Divergent. It's not just a job for either of us."

Today, Roth is a full-time writer living in Evanston, Ill. At 22, and a recent graduate from Northwestern's writing program, she fully appreciates Divergent's quick rise to success; HarperCollins printed 200,000 copies, and Divergent became an immediate bestseller. In the second volume in the Divergent trilogy, due out next spring, Roth promises readers more about the factions that weren't highlighted in the first book, and a lot more of Tris and Tobias.

Having readers react to Divergent has been a treat for Roth, though like many authors, she's had to overcome the initial anxiety of being in the spotlight. On a recent Dark Days of Summer Tour—with fellow authors Aprilynne Pike, Ellen Schreiber, Tara Hudson, Josephine Angelini, and Amy Plum—she met hundreds of teen and adult fans across five states. "Seeing people who are actually reading your book and listening to the wide variety of reactions they have to it," Roth says, "is really special."

When asked what message she hopes readers take away from her book, Roth is definite. "I want people to come away from my book with questions," she says. "Questions about virtue and goodness. Not answers."