Career clout can obviously go a long way in Hollywood, as demonstrated by "Young Adult," director Jason Reitman's (2009's "Up in the Air") and scribe Diablo Cody's (2009's "Jennifer's Body") honorably unorthodox follow-up collaboration to 2007's Oscar-winning "Juno." Without proven talents, it's hard to imagine Paramount Pictures green-lighting a project that steamrolls storytelling conventions and tidy personal arcs for a prickly-edged slice-of-life focusing on a character normally seen in movies saddled with the supporting part of a mean-girl antagonist. By keeping her as the central figure in every scene, the film fearlessly provides a sympathetic eye and ear to someone who gets off on being a tornado of chaos and probably doesn't deserve the viewers' sentiments. And yet, Reitman and Cody have once more made a career-topper so vividly real and pointed and achingly without compromise in its every last detail that one can't help but put a stake in where our unevenly-keeled guide, 37-year-old Mavis Gary (Charlize Theron), ends up, even as we must also frequently shrink down in our seats with dread over what we know she's capable of doing—and destroying. It's a tricky balancing act, likely even more difficult than it seems, in danger of becoming insufferable if not for perfecting the right mixture of observant humor and pathos.

To the folks of Mercury, Minnesota, Mavis Gary is a major success story. Twenty years ago, she was the most popular girl in school, and after graduation she ran away to the big city (Minneapolis, that is) and became a published author with a series of popular YA novels. In actuality, things aren't quite as rosy. She's divorced, rents a gloomy apartment in a nondescript high rise, drinks Diet Coke by the liter when she isn't downing shots, and is nearing the end of a writing contract now that sales have begun to falter. She isn't even credited on the cover of the books, but on the flap; she ghost-writes for someone with a bigger name and more pull, damn them. When Mavis receives an e-mail announcing the arrival of high school boyfriend Buddy Slade's (Patrick Wilson) newborn baby, she takes it not as joyful news, but as a cry for help. As she tells slightly confused friend Vicki (Hettienne Park) over lunch, Buddy must feel like a hostage, what with his boring job (ad sales at General Mills), his marriage, and now a kid tying him down.

Completely immune to the possibility that Buddy might be exactly where he wants to be, Mavis packs her bags, grabs her Pomeranian named Dolcé, hops in her Mini Cooper, and heads back to her hometown for what she fibs is "some real estate thing." As she goes about perfecting her outward appearance as a means of wowing Buddy and stealing him back, she finds herself becoming chummy with another former classmate, Matt Freehauf (Patton Oswalt). Despite having lockers right next to each other, Mavis has trouble remembering Matt until she accurately identifies him as "the hate-crime guy," an attack that left him permanently crippled and made national headlines until it was revealed that he was only mistakenly labeled as gay. Mavis wouldn't normally give Matt a second glance, but he's a good listener and only so happy to have her suddenly confiding in him about her wayward plans. Pretty quickly, it becomes apparent to everyone but Mavis that even as she edges closer to middle age, she still hasn't truly progressed beyond a 17-year-old mentality. Is it any wonder she listens to "The Concept" by Teenage Fanclub on a loop as she travels back to Mercury?

"Love conquers all. Haven't you seen 'The Graduate'?" asks Mavis, her tongue nowhere near her cheek. Just as she's misread the conclusion of that classic film, she is apt to do the same thing, over and over, in her own sorry life. In a burnt-black dark comedy far removed from the warm and fuzzies, "Young Adult" is a character study of uncommon originality and perceptiveness with a protagonist as fascinating as nearly any seen in 2011. She's a mess behind the scenes—unkempt, unreliable, and clinging to former victories—but when she's set to make appearances, you can bet four layers of make-up, shopping for a new outfit, and a mani/pedi aren't far behind. Rare moments of self-reflection, as when she is visiting parents Hedda (Jill Eikenberry) and David (Richard Bekins) and announces that she thinks she might be an alcoholic, are typically met with a brush of the shoulder and a laugh. The punchline—or is it tragedy?—is that she genuinely has a problem and could probably use some help that goes far beyond her drinking. How can Mavis learn about herself, though, if the image others project onto her are so radically skewed?

Audiences predisposed to expecting the usual narrative structure and neat endings where a flawed lead character becomes a better person are in for a rude, welcome awakening. The people around Mavis are seemingly normal, friendly sorts—Buddy and wife Beth (Elizabeth Reaser) are down-to-earth and caring, welcoming Mavis at the onset with open arms; Matt is a sports bar manager still searching for acceptance while dealing with injuries that continue to plague him every day; Matt's younger sister Sandra (Collette Wolfe), whom he lives with, is in awe when Mavis shows up on her doorstep—which somehow makes it all the easier for her to resent them. When the truth comes out from both sides—secrets that Mavis has kept inside herself, and the reality of how others in the town see her—it comes close to being just what she needs to reassess the mistakes she's made and the unhappy, unpleasant person she's become. In her mind, however, could it potentially be that she's just fine and it's everyone else that needs to change? For Mavis, it might take a few more eye-opening experiences for hers to finally stay open. That's simply her sad nature and destiny.

Outside of Diablo Cody's mature, pitch-perfect script and Jason Reitman's astutely revealing direction, one of the most crucial ingredients of the film is a lead actress who remains intensely watchable even when she's difficult to like. Living up to the promise of range and diversity she displayed in 2003's "Monster" and 2005's "North Country," Charlize Theron kills it in a very, very good way. Mavis is neither exaggeration nor cartoon, but she does exhibit some of the more unpleasant traits of humanity. She may or may not be capable of change, but as a woman both clueless and poignantly adrift in her own inflated ego, Theron's performance is one of the most complex and layered of the entire year. An unlikely confidante with the capability of loving her the way she wishes Buddy would, Matt Freehauf is brought to dynamic life by Patton Oswalt (whose largest film role, to date, has been voicing Remy the rat in 2007's "Ratatouille"). When Mavis downplays the extent to which he was harmed back in the day and tells him not to live in the past, it's a hypocritical slap in the face that Oswalt portrays with a bleeding heart. What is she doing if not living in the past? As Buddy and Beth, Patrick Wilson (2010's "Morning Glory") and Elizabeth Reaser (2011's "The Art of Getting By") present a happy portrait of a marriage that feels completely authentic to anyone paying attention. Naturally, Mavis views it as a fraud. With just a few scenes or beats apiece to make a mark, Collette Wolfe (2009's "Observe and Report"), as Matt's fawning sister Sandra, putting Mavis on far too high a pedestal for her own good, and Hettienne Park (2009's "Bride Wars"), as nonplused but agreeable Minneapolis pal Vicki, swing in, do their thing, and come away with unforgettable character vignettes of their own.

Mesmerizing in its understanding of small-town milieus and the accuracy brought to its view of interpersonal politics and stunted post-adolescence, "Young Adult" is like the twenty-first century's cinematic answer to 1999's brilliant Alexander Payne satire "Election." Relatable enough to earn laughter through the pain and non-judgmental enough to feel for every one of its characters, most of all Mavis, the film stands firmly on the line between earnestness and snarky irreverence without losing its equilibrium. At the home of Buddy and Beth, Mavis asks about a poster on the wall showing different emotions on cartoon faces. As a therapist for special needs children, Beth explains that it is easier for kids with cognitive issues to process feelings when they are able to see visual representations of them. Mavis nods and then asks how she would explain neutrality. It's the one she, and the kids Beth speaks of, are most familiar with. Later, when Mavis is faced with her childhood bedroom and all the snapshots and trinkets of her glory days, the simple act of finding an old red scrunchy and putting it in her hair is enough to break one's heart—and this is in regards to a person who is, for all intents and purposes, a selfish, unapologetic home-wrecker. That, above all, is the most astonishing achievement of "Young Adult," which deepens with every thought about it. Mavis is so real—in her voice, in her body language, in her often erratic actions and screw-ups—that it ceases to matter how "good" or "bad" she is. As a human being, she's struggling for the same things we all are; the picture, as deliciously tough and resolute as it is, isn't at liberty to give her a helping hand. What it can do is consider and accept her for who she is, and care. As much as Mavis would like to, there's no turning back the hands of time.