You may not have heard Veronica Roth’s name yet, but after this year you will. The Barrington High School grad had already landed a contract with HarperCollins before earning a diploma in English from Northwestern University in 2010. This month, the 25-year-old adds a notch to her belt with the release of the final book in her best-selling Divergent trilogy. Allegiant (HarperCollins, $12) comes out on October 22, just as postproduction on the movie Divergent (see below), draws to a close. “It’s a satisfying ending,” says Roth.

Roth’s trilogy is yet another entry in the young-adult genre that includes Stephenie Meyer’s Twilight and Suzanne Collins’s The Hunger Games. It’s a potential gold mine because, not surprisingly, teenagers relate to characters who navigate oligarchic societies run by overpowering adults.

Like the work of her predecessors, the first two books in Roth’s trilogy reached No. 1 on the New York Times children’s bestseller list, a testament to the loyalty of her teen fans, a famously fickle demographic. But while Roth’s name is often thrown into the arena with fellow YA novelists, few authors have written from so close to the epicenter: Roth was 22 when Divergent hit the shelves. “When I was a teen, my mom trusted me and gave me a lot of independence,” says Roth. “Now I think kids get pressured to make a decision about everything in their future.”

In some ways, the Divergent trilogy plays out like heightened lunchroom dynamics: You have to pick your friends, and at any moment you could lose your seat. In the first book, Roth introduces a society where citizens are segmented by personality traits: the bookish are named Erudite; the brave, Dauntless; the social, Amity; the honest, Candor; and the selfless, Abnegation. Tris, the 16-year-old protagonist, discovers she is a “divergent” and not suited to any one faction. By Insurgent, she is living as a refugee and gets caught up in a civil war. Allegiant is rumored to reveal a crumbling society, and Tris can see beyond its walls.

With the end of the series in sight, Roth says she’s eager for a little downtime. “I’m looking forward to playing around with some ideas,” she says, “but I know that I’ll write for teens, because I love them.”

If the Loop has seemed particularly dismal this summer, it’s because director Neil Burger was filming the postapocalyptic drama Divergent there. The movie (due out March 21, 2014) stars Shailene Woodley (The Descendants, left) and Kate Winslet (Contagion). Look out for a teeth-clenching Ferris wheel scene, a favorite of Roth’s.