The black town car pulled up and idled. White smoke curled from its tailpipe, rising in the morning drizzle. The driver stretched, his sportscoat tight at his back. He prepared for a wait. Within a minute, Veronica Roth, tall, with an angular, circa-1981 Pat Benatar haircut, high cheekbones and large Minnie Mouse eyes, bounded down the steps of her Edgewater apartment, still carrying her ceramic coffee mug. There was no time to dawdle. It was five days before the Tuesday release of "Allegiant," the final book in her phenomenally successful "Divergent" trilogy of young-adult novels about a dystopian Chicago and warring teenage factions. "I've been feeling really weird," she said, watching commuter traffic crawl west along I-88, sipping at her cup. "There are all these people who are going to read 'Allegiant,' right? And they expect something of me. They will want this series to end well. They have high expectations. Yet I have this feeling of impending doom. Or is it —" she raised an eyebrow — "impending awesome? There are a million copies of this book going out!" Actually, the first printing is 2 million. The car was sent by HarperCollins, her publisher, which needed Roth at the Aurora warehouse owned by the influential west-suburban Anderson's Bookshop chain. She was asked to sign 3,000 books — in one day. Some would go to the "Allegiant" midnight-release parties in Naperville and Downers Grove. There's the basic autographed stock that Anderson's, instrumental in developing Roth's popularity, needs to last through Christmas. Then there's the event with Roth that Anderson's is hosting Saturday at the Tivoli Theatre (an event that sold out months ago); at least 1,000 copies would be needed there. The town car stopped outside a stark office building buried inside an even more stark Aurora office park. Roth shouldered her way through the front doors and found a half-dozen Anderson's staffers buzzing about, smiling expectantly, busily stacking her books. On the first table were mounds of paperback copies of "Divergent"; on the next table, stacked row upon row, was its hardcover sequel, "Insurgent." But the bulk of the stock sat on the last table, tall, dense, skyscrapers of "Allegiant," its red, vaguely sci-fi cover repeating ad infinitum. "How it's going?" asked a burly Anderson's sales rep in blue fleece. "Good, if this is any indication," said Roth, her eyes calculating the task ahead. "Then don't look down," he said, sweeping his hand across dozens of boxes still unopened. There were 4,500 books to sign, not 3,000. Veronica Roth is the next YA superstar, a Barrington native whose first book hit big within a few months of her graduation from Northwestern University. Already established as a brand name within YA reading circles, she awaits that moment when she becomes a household name. Which looks like it could be any minute now … Mention her work to fans, booksellers and publishers, it doesn't take long before you're also discussing "The Hunger Games," "Twilight" and Harry Potter. "The kind of success Veronica has is unimaginable to most YA authors, who basically eke out $30,000 or so a year," said Robert McDonald, head of the children's department at the Book Stall in Winnetka. "Having her as a friend of this store is like having J.K. Rowling in your corner." Said Katherine Tegen, whose eponymous imprint at HarperCollins signed Roth in 2010: "I have such a strong gut feeling about Veronica. I mean, I was one of those people who could have (published) Harry Potter but management wouldn't let me spend large sums on it. And I've been haunted by that — until 'Divergent.'" Brian Monahan, a book buyer for Barnes & Noble's 674 stores, said: "This is the next series — the next to follow in that line of Stephenie Meyer's 'Twilight' and Suzanne Collins' "Hunger Games.' It is the next YA phenomenon. Historically, it's the third book in these teen properties that become the tipping point, and this one has already shown all of the hallmark signs: the steady growth, the online blogosphere-type buzz …" The coast-to-coast midnight release parties, the requisite "Today" show fluff piece from Ryan Seacrest. A week before "Allegiant" was released, pre-orders alone put it at No. 3 on Amazon's best-seller list; a few days before it was released, it was No. 1, the most pre-ordered title ever at HarperCollins, adult or young adult. Then there's "Divergent" and "Insurgent," which together have sold 5 million copies and been firmly entrenched at the top of the New York Times' young-adult best-seller list for months. And, of course — because it wouldn't be a successful young-adult series without a Hollywood movie attached — "Divergent," the first of a planned series of adaptations starring It Girl Shailene Woodley, wrapped production in July. The film, which shot around Chicago in the spring and summer, opens March 20, 2014. All of which, relatively speaking, makes 4,500 books to sign a drop in a pop-culture ocean. And yet, at the heart of this phenomenon is a person who is only 25 (she sold her first book to HarperCollins at 21), who has persistent anxiety issues, who is dealing with rabid admirers, who is figuring out where the line is between personal and public life and who, she said, still feels she's leaning to write. John Green, himself a wildly successful young-adult author (and resident of Indianapolis), has been Roth's frequent sparring partner on the Times best-seller list — his blockbuster novel, "The Fault in Our Stars," is even becoming a movie starring Shailene Woodley. On the phone from Amsterdam, where that film is currently in production, Green said: "I think Veronica is handling herself as well as she can, considering everything. At 25, I couldn't remember to pay rent. And the truth is, no one tells you that this kind of success will be intimidating. But it is. It's a massive amount of pressure, and not just from fans, but from people whose jobs are on the line because of what you write. There is pressure from publishers to grow the YA space, which has been one of the few bright spots in the publishing world for the past decade. You start to realize you could disappoint millions of people — you could not understand what it feels like until you experience it."

"I'm going to throw up." Last April, Roth and her husband, Chicago photographer Nelson Fitch — with her agent, Joanna Volpe, in tow — were gassing their 1994 Mercedes on the way to the West Side set of "Divergent" when Roth became very anxious. The film rights sold in 2010, soon after the book rights, and Roth didn't want anything to do with the creative end of the film, not the screenplay and not the casting. She said she's a writer, not a filmmaker. And yet, here was a film based on writing she did at Northwestern. Still, brand-wise, it doesn't always matter if the author had anything to do with adapting the material — failure and success reflect equally. She should at least visit the set. When she arrived, there was a director's chair with her name on it. As she looked across the set — a giant fighting arena with white squares on the floor matched by white overhead lights — she became misty-eyed. "It's like walking into my brain," she marveled. Theo James — the actor playing Four, the love interest to Woodley's Tris, the series' brave, questioning heroine — burst past them, dressed in full costume. Roth and Volpe looked at each other: He's totally Four. The "Divergent" series takes place in Chicago sometime in the future (not until "Allegiant" do we get a clear sense of when). Chicago has become a crumbling gated community of sorts, its citizens divided into factions defined by personality traits, their clothing coded by clan: There's Dauntless (bold), Abnegation (selfless), Amity (peaceful), Candor (honest) and Erudite (intellectual). At 16, Chicagoans decide what faction they want to be associated with, the one they were born into or one they aspire to. There's also the non-faction faction, the Divergent: the rebels who don't fit in. It's a classic dystopian set-up: a genetically engineered society pits teenager against teenager, then collapses, leading to a civil war. With a few goofy, naive touches: There's a villain named Jeanine. Also, truth serum is involved. (Yes, truth serum.) Nevertheless, if you're a young adult, or have a young adult at home, you know: Dystopias are hot. Roth, who said she had not read "The Hunger Games" until after she had written "Divergent," was a longtime fantasy-sci-fi reader and fan of Lois Lowry, whose 1993 novel "The Giver" has become a contemporary dystopian classic. "The funny thing is, when I met Veronica, 'paranormal romances' were buzzy in YA," said Volpe, who said that she pitched "Divergent" to publishers as a "futuristic thriller" because "sci-fi" was not selling at the time and "The Hunger Games" had not yet made "dystopia" the hot, fashionable genre. Molly O'Neill, then a new editor at Tegen (with a marketing background), took the bait: "Everyone would compare it to 'Hunger Games,' we were aware, yes. It would be regarded by some as a read-alike. But really we were reacting to the story. I was pitched on a Thursday night, started reading it on the subway home. Two stops later I had goose bumps. By the time my train reached Brooklyn, I was texting to cancel my dinner plans." Roth always liked the way that children's books played with categories — how Harry Potter novels, for instance, divided characters by their magical dormitories. And HarperCollins liked how her factions could be a savvy marketing hook: Which faction would you be in, dear reader? Still, read-alike or not, "Divergent" makes for a clever parable about growing up, its factions serving as stand-ins for social groups, Tris' conflict with the factions a thoughtful vehicle for showing how a complex person is more than one defining trait. "Simplicity is easy to come by," said screenwriter Evan Daugherty, who wrote the "Divergent" screenplay. "But a simple thing done well is hard to beat. Veronica nailed a very primal, relatable idea: You turn 16 and you choose what you think is going to be some narrow version of how the rest of your life is going to look." Roth said that she's been told by fans and critics that the series is about everything from high school cliques to standardized testing to a moralistic religious allegory. A moralistic, devout Christian herself ("but not in a creepy way"), Roth said: "People assume there's some weird indoctrination thing hidden in these books, because the assumption is if you're Christian, you're preachy. But that would be a horrible thing to do to kids." Still, asked if there was deeper meaning intended, she added, simply: "It's a personal critique." Roth began writing Tris, her daring heroine, because she herself was anxious. "Because of the anxiety, my own life felt repressive. So just as Tris makes bold moves and leaves her repression, I did bold things: I got married young. I moved to Romania for a while. I cut my hair short. Like Tris, I am trying to be a richer, fuller version of myself." Roth said she's been diagnosed with a generalized anxiety disorder. Last year, after "Insurgent" became a best-seller, proving that the series was not a one-book sensation, she was treated with exposure therapy — a technique that presents an anxiety-disorder sufferer with the root of their anxiety. Which, in Roth's case, was the Internet. Going online for anything had become "a minefield" of one-star Amazon reviews and snarky messages about how she "writes like a fourth grader." She said that she has since learned to manage the trolls; she still gets upset but doesn't let it paralyze her now. The bigger problem now is the intensity of fandom: readers who meet her and break into tears, fans who follow her for autographs. At the National Book Festival in Washington she became upset when faced with the task of signing and meeting 1,100 fans in one hour. "Some fans wait, like, five hours. You want to make it worth their time. Now I'm disappointing 700 people." Not coincidentally, other than Chicago, her book tour for "Allegiant" will stop in only four cities. Said Margaret Stohl, co-author (with Kami Garcia) of the popular "Beautiful Creatures" YA series: "The first time I met (Veronica), a couple of years ago, 'Divergent' had just come out. I already saw that familiar deer-in-the-headlights look, the freight train was bearing down. I said, 'Are you OK?' And she said, 'That's funny. Everyone just says "Congratulations."' I said, 'No, I understand: There's bad traumatic and good traumatic.' See, YA is partly a cult of personality. Could you imagine if you could contact (children's author) Richard Scarry? As a child myself, I loved (children's author) Susan Cooper, but I couldn't tell you what she's like. Veronica's fans, they think she's beautiful, read her blog, send her messages. It's a new world."