Anne Hathaway looks like a movie star, but more often than not acts like a studious, earnest head of the class. Rather than filtering characters through some kind of star persona or actorly invention, she does what is required with such technical precision that her performances lose any spark of spontaneity (that's why she didn't get any laughs playing Agent 99 in Get Smart; she somehow managed to play the straight woman role too straight).

But something happens in Jonathan Demme's Rachel Getting Married. Hathaway plays Kym, the black sheep of an upper-middle-class Connecticut family who has left rehab in time to attend her sister Rachel's wedding. This isn't simply a case of an actress obviously playing against type, although she clearly is. Hathaway teases her studiousness out into self-centered, self-destructive prickliness; Kym is like a teacher's pet, begging to be rewarded for her self-aware (but caustic and uncomfortable) humor, and her self-serious (yet somehow pompous) parroting of Narcotics Anonymous wisdom.

It's a tightly wound character, but playing her loosens Hathaway up, and she nails every self-involved gesture, down to the way a cigarette constantly dangles from Kym's lips, as if to extend as far as possible into others' space, a reminder that she's allowed this one addiction because she's been through so much worse. You may have discerned that Kym isn't remotely likable, but the wounded, weary contentiousness of her relationship with fed-up bride Rachel (Rosemarie DeWitt) works up a lot of empathy.

The action is confined to a few simple locations over the course of the weekend, peppered with regular confrontations and the revelation (at least to the audience) of a dark secret. The narrative of Rachel Getting Married resembles a play, and not a terrific one. Demme seems to want an experience even more intimate, filming Jenny Lumet's script with handheld cameras, aiming for a home-movie texture. The result isn't always that kind of striking immediacy; sometimes, it's just a semi-verite movie supported by oddly stagy coincidences, like the identity of a man at a Narcotics Anonymous meeting, or the placement of a key dish in the kitchen.

The wedding rituals themselves fit Demme's aesthetic the best, because he runs his camera and allows us to see what a wedding guest would see: not one but four or five toasts, people who aren't formally introduced, and lots of musical performances. It's all very warm-hearted, but after awhile, the sheer volume and diversity of life-affirming music at this one little wedding begins to feel a little like an NPR festival curated by a famous movie director. Rachel's new husband Sidney is even played by Tunde Adebimpe of the band TV on the Radio; it's reasonably easy to imagine that Sydney is the guy from TV on the Radio, not only because of his parade of musician friends, but because the movie fails to supply him with another personality.

So it goes with many of the supporting characters, and this may be intentional, to keep the film's focus tight and compelling. Kym and Rachel are certainly well-drawn and beautifully played, as are their divorced parents; Bill Irwin and Debra Winger find exactly the right points of familial routine, making alliances and fractures utterly visible.

That kind of grace makes Rachel Getting Married involving, and worthwhile. But despite the sense that Demme himself is throwing the party, the movie itself never feels especially personal, and its thoughts on forgiveness and dysfunction are thorny and without a lot of depth (it also resembles an unfunny, more conventionally 'likable' version of Margot at the Wedding). Lumet may yet write a terrific movie (or play); this one is a little too weepy, too circular. All of which, in the meantime, makes Hathaway's work all the more impressive: She's learned to run with her material, not just keep pace.

The DVD includes deleted scenes, two commentary tracks, a cast and crew interview, and a behind-the-scenes featurette.

I thee wed!