Hathaway in "Rachel Getting Married"

Jonathan Demme's "Rachel Getting Married" has a loose, improvisatory feel that gives you the impression you're eavesdropping on an actual wedding, but the casualness of the style is deceptive: this is one nerve-racking celebration. The source of the movie's unease is Kym, played by Anne Hathaway. She's the sister of the title character (Rosemarie DeWitt), and she's just gotten out of rehab to attend Rachel's wedding at their father's house in an upscale Connecticut suburb. Kym, like most junkies, is a master of manipulation and a monster of self-absorption. Everything is about her: when she stands to give a wedding toast on the eve of the nuptials, she offers instead a rambling, narcissistic AA-style confession. She insists that she, and not her sister's best friend, be the maid of honor. Rachel is enraged: she's all too familiar with her sister's attention-hogging self-destructiveness.

Anyone expecting the demure, doe-eyed Hathaway of "The Princess Diaries" or "The Devil Wears Prada" is in for a shock. Kym is a major pain in the ass, and Hathaway's raw, spiky performance makes no attempt to ingratiate. Yet she makes Kym's inner torment so palpable you can't help but feel for her, however insufferable she may be. It's a terrific performance, and DeWitt matches her step for step: you can feel a lifetime of tangled sisterly feelings in every charged moment between them. "Rachel Gets Married" is messy and misshapen, but boy is it alive. It has some of the quirky, unpredictable humanity of Demme's early, best work, and its teeming, spontaneous frames pay explicit homage to Robert Altman. Shot with a jittery, handheld, high-def digital camera by ace cinematographer Declan Quinn, the movie has the feel of a slightly hallucinatory home movie.

First-time screenwriter Jenny Lumet's script weds a unpredictable countercultural sensibility to a dysfunctional family melodrama. It's not always an easy fit, but it keeps you on your toes. The wedding is a multicultural affair: Rachel's future husband, Sidney (TV on the Radio lead singer Tunde Adebimpe) is black. He works in the music biz, as does Rachel and Kym's father, Paul (Bill Irwin), which accounts for all the hipsters and musicians at the wedding party. Paul is divorced from Kym and Rachel's mom (Debra Winger, making a welcome return to the screen), and his new wife is African-American (Anna Deavere Smith). But race is a non-issue in the movie—it's never even mentioned, which is probably an accurate reflection of the artistic world Lumet grew up in: her father is director Sidney Lumet; her mother, Gail, is the daughter of Lena Horne. Part of what makes "Rachel" feel fresh is the specificity of this upscale boho milieu—it's a world rarely depicted in movies, and Demme, who mixes actors and musicians and friends in the cast, films it with great affection. Perhaps too much so. The downside of the home-movie style is a tendency toward self-indulgence. The director is so enamored of his world-music bands that "Rachel" sometimes stops in its tracks and threatens to become a concert film.

Under all this culturally specific detail are the bare bones of melodrama. Lumet saddles Kym with a family-tragedy back story that wouldn't be out of place in a daytime soap opera, and at least one scene—when a comic scene suddenly turns hushed and somber when the father is reminded of this tragic event—rings false. But these are easily forgiven lapses; most of the time, Demme's deliberately unstable mixture of moods and genres produces electric results. "Rachel Getting Married" takes a familiar subject—the raw nerves of American family life with—and draws fresh blood.