How complicated is the back story for Another Happy Day, you ask?

So complicated that the first five minutes of the movie consist of one character filming an “interview” of another character about it, for no apparent reason (beyond lack of a better way to clarify it to an audience). And I’m still not sure I followed it all. But I’ll give summarizing it a shot…

Middle-aged, high-strung Lynn (Ellen Barkin) has two kids with her benign first husband Lee (Jeffrey DeMunn), one of whom, the utterly non-descript Dylan (Michael Nardelli), is getting married, thus bringing the whole family together for the weekend, including Lynn and her two sons from her second marriage to the abusive Paul (Thomas Haden Church), who is now married to trophy-ish Patty (Demi Moore).

Paul and Patty mainly raised Dylan, for reasons never made clear (see?), while the other older child, Alice (Kate Bosworth), was raised by Lynn but has spent many years in therapy due largely to a nasty habit of cutting herself, and thus hasn’t seen Paul in years. Lynn’s two younger sons (with Paul? I think?) are the pudgy, Asperger’s-stricken Ben (Daniel Yelsky) and drug-addicted, Tourette’s-suffering, gender-confused, and general malcontent wise-ass teenager Elliott (Ezra Miller), but Lynn is far more concerned, for reasons unclear (see?) about how seeing Paul after so many years is going to affect the emotionally fragile Alice.

Still with us? Because I haven’t even gotten to Lynn’s mom, the rigid and judgmental Doris (Ellen Burstyn) who not only has to cope with Lynn’s tantrums but her half-demented Alzheimer’s-victim husband (George Kennedy) whose health is erratic and who has a habit of wandering off into the woods. And did I mention Lynn’s gossipy, giggly sisters (Siobhan Fallon and the delightful Diana Scarwid)? (And yes, we meet their spouses and kids as well…)

So yeah, there’s a lot going on, so much so that practically every scene in this two-hour movie contains a confrontation, many of which lead to punches being thrown or tears being shed, or both. It has the enormous ensemble cast and countless, overlapping plot threads of a Robert Altman movie, but the soul of several Lifetime MOWs blended together. That it winds up working to the degree it does is a tribute to the burgeoning talents of writer-director Sam Levinson, whose father Barry gave Barkin one of her breakout roles in Diner (another, way better multi-plot ensemble movie that culminates with a wedding).

The younger Levinson has clearly inherited dad’s ear for sharp, naturally quirky dialogue, but he seems to have taken too literally the Screenwriting 101 advice that every scene must have CONFLICT. Every five minutes, one character corners another (sometimes, rather unbelievably, in front of a crowd of relatives and guests), demanding to know “Why do you treat me that way?” or “How come you never take my side?” or “Why does everything have to be about you?” And bizarrely, the much-delayed meeting that gets the most set-up time devoted to it, that between Paul and Alice, turns out to be just a fizzle. But hey, if one confrontation doesn’t grab you, just wait a few minutes for the next one.

Fortunately, Levinson wisely cast his movie across the board with actors capable of selling this material. Twenty years ago, Barkin (who also produced) was one of the most intriguingly sexy leading ladies of the 80’s, and after a long stretch of minor roles since then, it’s great to see her front and center, aging gracefully and still milking that inimitable half-smile for all its worth. Moore, speaking of 80’s leading ladies, does her best work in years as well, her sculpted figure and seemingly innate bitchiness quite appropriate for the character. Former Oscar-winners Burstyn and Kennedy are welcome representatives of the previous generation (Kennedy, at 86, looks like he could still be digging away alongside Cool Hand Luke).

Church pulls off the most difficult challenge, playing a character whose inability to entirely put his despicable past behind him evokes an equal mix of sympathy and disgust.

But the movie is all but stolen by Ezra Miller, who, with this and We Need to Talk About Kevin, is on the verge of indie It Guy status. Elliott has enough issues for two or three characters: Above and beyond the usual teenage angst, misanthropy and self-destructiveness, his Tourette’s has him constantly on the verge of an uncontrollable rage, and he spends half his time in the bathroom, either half-comatose from popping Grandpa’s pain medication or exploring his feminine side. He’s such a bizarre but somehow likable mess that he demands our attention right from the beginning.

As the family’s resident smart-ass, he also gets all the best lines. In one of the movie’s few quiet scenes, he muses, “What is it about weddings? If this were a funeral, we’d all be being nice to each other. Apparently, death creates more family bonding than love.”

Indeed, what is it about weddings? With this movie, Rachel Getting Married and Margot at the Wedding (both 2008, within what seemed like days of each other), American indies have now redefined these seemingly joyous occasions as ruthless scab-rippers, as malevolent catalysts for decades of familial tensions, rivalries, jealousies and secrets to boil over. Another Happy Day, thanks to its cast, its strong dialogue, and its never-a-dull-moment zip, is probably the best of the three, but it’s ultimately too crowded, its conflicts too on-the-surface to be entirely satisfying or believable. Young Levinson clearly has chops, but he could use a little more of his dad’s lighter touch at the keyboard. Barry should send him to his room without any supper to watch Diner and Tin Men again.