“Divergent” gives us a spunky young heroine finding her way through a treacherous world whose population is divided into rival castes and ruled by authoritarian administrators. No, not high school. The film is the first in a planned post-apocalyptic trilogy based on Veronica Roth’s novels (and, let’s be candid, “Harry Potter,” “The Hunger Games,” “Ender’s Game” plus a dash of Orwell).

It’s a middling effort. Shailene Woodley (“The Descendants”) stars as Beatrice, who faces an existential coming-of-age crisis in the war-ravaged urban oasis of future Chicago.

At the annual Choosing Ceremony, should she remain a member of Abnegation, her charitable birth faction, whose members presently hold the reins of the society’s power? They’re good and all, but tiresome, eating sprouts and mincing about in pigeon-gray vestments that are about as flattering as the average bathrobe.

The other options include the brainy Erudite, ever-truthful Candor, hippy-dippy Amity and brave Dauntless, who police the walled city. You don’t want to be Factionless, whose main duty is to cluster on street corners and look like wretched derelicts.

Before the big decision, initiates undergo a brain scan to assess their strengths. Beatrice’s personality profile makes her tester blanch. She is a rare Divergent, with several natural gifts and as such a threat to the social order. The results are hushed up. Beatrice joins the Dauntless, whose gung-ho spirit, tats and body-conscious leather uniforms look pretty rad, and crops her name to Triss. She hops the elevated train to HQ like the rest of the Dauntless crew traditionally do, by running full speed beside the rolling cars and leaping in. Whether it stops for the other classes is never explained.

Cue the training montages where the transfer student learns that it takes a lot of practice and pain to make the cut. Especially while getting the tingles from hunky Instructor Four (Theo James). The nemesis here is Jeanine (Kate Winslet), a power-suited Erudite of frigid intelligence. Her smile is like sunlight glinting off a casket handle. The performance is nicely underplayed, chilling us through good manners and crisp diction. Like the endlessly watchable Woodley, she gives this pulpish material her full attention and craft.

Ashley Judd makes every scene count as Beatrice’s mother, whose character also resists categorization. Director Neil Burger rightly frames them in adoring close-ups. They’re the movie’s almost-saving graces. Acting honors among the men go to Miles Teller (Woodley’s co-star in “The Spectacular Now”) as a hissable chauvinist classmate. When his comeuppance arrives, it’s one of the film’s most emotionally effective moments.

A movie like this doesn’t require a lot of tonal variety to succeed, but imagination is crucial. The “Hunger Games” films are grim but full of high-wire thrills, colorful characters and ambitious production design. Here, Triss struggles amid industrial decay with a palette stretching from concrete to rust. There’s a monotony to the pacing, and the intricate social structure is all but forgotten as the story plods ahead.

Like the accursed “Star Wars” prequels, “Divergent” foregrounds the background, prizing world-building socio-historical blather over adventure. The third-act confrontation with an evil faction making a power grab could have been an exciting chess game with each bloc exploiting its particular strengths. Instead, every clash is settled with commonplace shootouts.

A scene where Triss is subjected to a drug-amped phobia test, which should have the gut impact of “1984’s” Room 101, plays like a quick session of “Angry Birds.” That’s the movie in a nutshell: “Divergent’s” not urgent.