I’ve long had an obsession with movies about unrepentantly shitty people. There’s something about the manipulation of an audience’s natural identification with a protagonist just because they’re the protagonist that’s made so much better when it’s forced to place itself within a horrible human being. Too frequently, though, such films yield in the third act, and in order to prevent absolute discomfort pull a select few punches for the sake of providing some sort of emotional landing pad. Young Adult not only refuses to let up on its subject, but actively sends her even further into the void before it’s through.

Mavis Gary (Charlize Theron) is in her late 30s, a successful author of a long-running young adult lit series about catty teens in a prep school and miserably alone. There’s really nobody else to blame for this; it’s clear she discovered at a young age that natural beauty and a stabbing glare was all she needed to get where and what she wanted, and held on to both for dear life. When she gets an email announcing that her high school sweetheart Buddy (Patrick Wilson) has started a family, she heads back to her native land of Mercury, Minnesota to reclaim him, and not his wife or his child or any sense of moral decency will stop her.

Young Adult is a welcome left turn for the writer-director tandem of Diablo Cody and Jason Reitman. They last collaborated on the insufferable, inexplicably beloved Juno, and that film and this one could not be more diametrically opposed. Here, they’ve created less of a comedy, or even the seriocomedy that’s become Reitman’s signature, than a meticulously observed character study about people trapped in stasis, railing against their surroundings in a last-ditch attempt to get back to a point when they felt “at their best.” Mavis may have dug her own grave in small  increments, but what’s really ruined her is that she buries down her rare lucid moments under several layers of bourbon and self-righteous indignation. For Mavis, she is still the high-school alpha queen, the girl who was elected prom queen at a school she didn’t attend, and this cannot and will not change.

Her week in Mercury, though, is an excruciatingly uncomfortable immersion in her myriad flaws. A good number of these realizations come from Matt (Patton Oswalt), a former classmate with demons of his own. Where Mavis wants nothing more than to go back to 17, Matt has spent his life trying to escape. More than anything else, the bond they forge is mostly due to their shared inertia, and the toxic reservoirs of anger and loathing, inward and outward, that sustain them. Simultaneously, they’re both bought out of their personal cloisters just for the welcome departure from normalcy that the other provides.

This film wouldn’t work without a pair of willing, virtually fearless actors, and Theron and Oswalt are both stunning. Oswalt, who broke through with Big Fan, gives a career performance as a partially crippled, angry man who finds solace in cynicism and geekdom. Theron, meanwhile, is magnetic no matter how deep she sinks (and the depth is profound, by film’s end), not allowing Mavis to gain any more empathy than she deserves. This is a breathless feat of acting, one that holds no regard for charm, vanity or general likability. Young Adult, too, is a rare movie, brutal and uncomfortable and completely true to its core. These people will never grow up, and yet, as a painful moment late in the game suggests, the balance of the world may depend on them staying right where they are.