Couples planning wedding ceremonies may want to skip “Blue Valentine,” at least until after they’re actually hitched. Derek Cianfrance’s film is a brilliantly naturalistic dissection of romance and marriage, one that ends in a defiantly anti-Hollywood fashion that may leave lovebirds in the audience reconsidering their matrimonial plans. But for others this powerful domestic drama will carry a welcome, if uncomfortable, dramatic wallop.

Ryan Gosling and Michelle Williams play Dean and Cindy, who meet when, as part of a moving crew, he helps an elderly man move into the nursing home where her grandmother is a resident. He literally pursues her and wins her over, though she’s a middle-class girl with ambitions to go to medical school while he’s an amiable young drifter without prospects—and she already has a boyfriend named Bobby, a possessive fraternity guy with a volatile temper. She’s also pregnant, though she hasn’t told Bobby; and when she breaks up with him, he takes it out on Dean, who’s happy to raise the child with Cindy as his own.

The story of the couple’s budding relationship is intermingled with scenes from their later married life, marked by economic and personal stress. Dean’s basically a pleasant fellow and a doting father, but he’s essentially a carefree guy unconcerned with practical matters—something that irks Cindy, who works in a doctor’s office and is becoming increasingly angry over her husband’s failure to provide security and a better life. The situation is exacerbated by Cindy’s chance meeting with Bobby and her boss’s (Ben Shankman) offer of a job that would require her to move. And when Dean tries to smooth their problems with a getaway to a shabby motel, it only makes matters worse.

What’s remarkable about “Blue Valentine” is its overriding sense of authenticity, something that derives not only from the carefully calibrated script and atmospheric production (sensitively designed by Iribal Weinberg, with fine assists from set decorator Jasmine Ballou and costumer Erin Benach), but from the extraordinary performances by Gosling and Williams. He succeeds in fashioning a figure so truthful—an ordinary guy satisfied with scraping by from day-to-day without overexerting himself—that you may feel you actually know him, while she convincingly paints a portrait of seething frustration over her lot in life. Their scenes together—a few fairly explicit, which originally got the picture an NC-17 rating (unfairly, in view of the studio tripe that gets “R”s regularly)—exhibit an amazing rapport and emotional honesty.

If there’s a flaw in the screenplay, it’s that while Cindy is provided with a family background involving a rigid, volatile father (John Doman) and supportive grandmother (Jen Jones) that helps explain her fragility, Dean’s earlier life is left vague, revealed mostly in a single dinner conversation that gives us only the barest sketch.
There are also episodes in “Blue Valentine” that take a fairly conventional route. One might wish, for example, that Cianfrance had avoided the sequence in which Dean and Cindy get to know one another by acting cute while taking a nighttime walk, despite the fact that Gosling and Williams carry it off with an unforced charm that suggests much of it was improvised; and the entire subplot involving Bobby has a standard-issue feel.

But for the most part this is a meticulously observed, intensely realistic portrait of a relationship that—like so many—fails to last. But the memory of it is likely to stick with you, whether you like it or not.