"Young Adult," the new collaboration from "Juno" director Jason Reitman and writer Diablo Cody, shares some stylistic notes with their earlier effort. It's set in Minnesota, features a pop-saturated soundtrack (including the Replacements), a woman-child stuck between adolescence and adulthood, and a droll appreciation of daily life in suburbia. Yet it's a step in a new direction, both for the creative team and for movies, a mature and humane comedy centered on a misanthropic female antihero.

Think of it as "Juno's" wicked stepsister.

Charlize Theron plays Mavis Gary, a divorced writer (or as she prefers it, "author") of "Sweet Valley High"-style teen novels. Though she's 37, Mavis never really graduated from high school. Her Minneapolis high-rise apartment has the depressing, slumlike impermanence of a crash pad. Her social life consists of bad overnight hookups and lunches spent belittling former acquaintances with a catty former classmate who fled Mercury, Minn., for the big (well, biggish) city.

At once haughty and insecure, Mavis is a textbook case of arrested development. To top it off, she's still obsessed with her former high school sweetheart, Buddy Slade (Patrick Wilson). Her fixation flares when Buddy's wife e-mails her an announcement welcoming their newborn child.

Mavis launches a mission to rescue Buddy from the bondage of family life, heedless of the fact that he's utterly content as a new dad. Equipped with an armory of makeup brushes, falsies and lethal little black dresses, she travels back to her hometown to reclaim her man. The comedy of awkwardness is honed to a stiletto edge. When two-faced Mavis, in slinky cocktail attire, seductively wheedles Buddy at a plaid-shirt sports bar, she's as out of place as a black widow on a slice of apple pie.

Looking on mockingly is Matt (Patton Oswalt), a wisecracking former classmate of Mavis and Buddy's. Though he's physically disabled from a brutal high school bullying attack, he's better adjusted than Mavis. As she pursues her romantic delusion to its bleak conclusion, the two misfits strike up an unlikely friendship. In Matt, Mavis discovers the one confidant who might have saved her from terminal self-absorption, if only she had met him when she was still young enough to change.

Edgy, subversive and hilariously embarrassing, "Young Adult" undercuts the conventions of female-centered comedies at each turn. It manages to keep us invested in the story despite focusing almost every scene on a thoroughly unpleasant protagonist. The supporting characters provide the homespun humanity Mavis lacks, especially Wilson as her Minnesota Nice former beau, and Elizabeth Reaser as his fun-loving wife.

Theron scores with a brave, darkly amusing performance as a onetime alpha female who sees life passing her by. She smiles charmingly while shooting death rays from her eyes. In her scenes with Oswalt, Theron drops her character's mean-girl bravado, revealing the fear, loneliness and confusion beneath her Revlon mask.

"Young Adult's" skepticism that Mavis can fan these flickers of self-awareness into a flame of understanding is a gauge of its sophistication. Cody and Reitman would rather close their film on a lifelike, unresolved note than force its characters into a contrived happy ending. Audiences may not embrace Mavis immediately -- she's too spiky for that. But there's little doubt that in time she'll join Marge Gunderson and Juno McGuff as another of Minnesota's enduring and iconic film characters.