It’s rare that a movie is as good as the book on which it’s based. It’s even more unusual when it’s better.

With the film adaptation of “Divergent,” the first novel in Veronica Roth’s trilogy of dystopian thrillers, director Neil Burger (“Limitless”) has crafted a popcorn flick that’s leaner, more propulsive and more satisfying than the bestseller that inspired it. Screenwriters Evan Daugherty and Vanessa Taylor have cut the fat, picked up the pace and sharpened Roth’s themes celebrating individualism and ingenuity, which were muted in Roth’s somewhat sluggish and overlong telling. Daugherty and Taylor have even come up with an ending that more cleverly utilizes the story’s teenage heroine Tris (Shailene Woodley) without changing the outcome.

It’s still cliffhanger-ish, in a way that makes this first installment of the trilogy feel more like an appetizer than a full meal. But the movie’s plot tweak alleviates the sense of mild disappointment generated by the book’s conclusion.

Set in a post-apocalyptic Chicago that is walled off from the rest of the world by a massive rampart, “Divergent” imagines a society in which the citizenry is divided into five monolithic factions according to personality. Municipal government is controlled by the Abnegation faction, an ascetic class given to self-sacrifice and altruism. Candor runs the courts; Amity, a commune of hippielike agrarians, works the fields; and the Erudite pursue scientific advancement. Security is left in the hands of the Dauntless, a group of soldiers so intrepid they might better be called the Young and the Reckless.

It’s the Dauntless faction that Tris joins when, at 16, she is allowed to declare a new allegiance. Although all adolescents are given aptitude tests to determine factional affinity, they are also allowed the opportunity to remain in the community of their birth or to select another, even if the test indicates they are not suited for it.

As you may have guessed by now, Tris — by birth a member of Abnegation — is “divergent,” meaning that she has equal aptitude for more than one faction.

Although that makes her merely human, it also means that she’s harder to corral and must hide her capabilities. In the world of “Divergent,” it’s human nature that got people into the mess they’re in. Segregating them into neat little pods, not by color, but by character, seems as good — or as bad — a solution as any.

Silly, I know. But the film actually does a pretty good job of articulating this rationale. If the absurd premise sticks in your craw, stay away. All others, sit back and enjoy the parable.

The first part of the film focuses mainly on Tris’s initiation as a member of Dauntless, during which time her unusual skills draw attention, both wanted and unwanted. A handsome, brooding trainer known as Four (Theo James) takes her under his bulging biceps, even as Tris earns closer scrutiny from some jealous recruits.

Later, Tris’s contrariness catches the eye of the evil Erudite leader, Jeanine (Kate Winslet), who is plotting a coup against Abnegation with the help of an army of doped-up Dauntless robots.

Visually, “Divergent” delights, creating a believably decaying Chicago and using a palette of black, white, blue, gray and saffron costumes to delineate the five factions’ uniform-like clothing. Woodley also makes for an appealingly complex Tris, a heroine whose sense of loss at leaving her family behind — along with her sense of identity — is tempered by the thrill of discovering new powers, both moral and physical.

The book spent a lot of ink exploring the romance between Tris and Four. Even if it didn’t use that relationship to define the young heroine, it seemed to be saying that sexual awakening is as much a part of Tris’s journey as anything.

There’s nothing wrong with that, but the movie serves up an even more fully fleshed version of Tris. She’s fascinating for what she does, not merely for whom she likes.

★ ★ ★

PG-13. At area theaters. Contains violence, some obscenity and disturbing thematic material.
130 minutes.