You know you’re in for a lively evening when a play about a family reunion includes a fight director among the team. And how satisfying that he’s called Chuck, too. Tracy Letts’s blisteringly funny, unsettlingly dark August: Osage County was commissioned by the celebrated Steppenwolf Theatre Company of Chicago, then transferred to Broadway a year ago to rapturous acclaim, winning a Tony and a Pulitzer. Now Steppenwolf has brought it to the National Theatre, and you can see exactly what all the fuss is about. It’s terrific.

Beverly and Violet Weston are the father and mother to three middle-aged daughters, and growing old disgracefully. He’s a drunk and she’s a pill-popper, but they’re no trailer trash. They live in a fine, though decrepit, house in Pawhuska, Oklahoma (60 miles northwest of Tulsa, if you must know), and he is a literate and intelligent, though bitterly disappointed, devotee of TS Eliot and John Berryman. Beverly’s lifelong cloud of unhappiness may have to do with the fact that, as we later learn, between the ages of 4 and 10 he lived in a Pontiac sedan. Onepowerful theme among many here is that today’s baby-boomers have no idea how tough life was for their parents. “So they were poor and hated Nazis,” says Barbara, the eldest, toughest daughter, scornfully. “Who doesn’t hate Nazis?” Yet the theme carries weight.

Violet is a true monster mother. The fact that she and her sister, Mattie Fay, endured the sort of childhood in which their mom’s boyfriend regularly attacked them with a claw hammer only vaguely explains her lacerating, gleefully destructive attitude towards her daughters. Her idea of time well spent is to steadily destroy their self-esteem with an acid drip of criticism and contempt that leaves them flayed and trembling — then really lay into them. There’s mention of Bette Davis here, and Violet does remind you a little of What Ever Happened to Baby Jane?. Brilliantly played by Deanna Dunagan, with short-cropped hair and twisted smile, she also reminded me distinctly of Anne Robinson.

Add to this scenario incest, adultery, cancer and suicide, and you have a mix that only the most skilful and empathetic dramatist could make funny and moving, rather than merely cold-hearted, manipulative and dispiriting. Letts’s work, however, is a triumph. We laugh with the characters and they laugh too, despairingly, trapped in a kind of particularly nightmarish Chekhov of the plains.

The most engaging character is the sharp-tongued, clever Barbara (Amy Morton), although this is essentially about superb and generous ensemble acting. Female friendship and sisterhood are sharply portrayed as a dense minefield of resentments and jealousies waiting to explode. Women are ruthlessly competitive, more likely to assert themselves by demolishing a rival than by achieving their own success. Karen, the youngest daughter, is a perfect study in how self-absorption simply dooms you to a life sentence of nervy misery.

Men fare no better, however. You can spot her fiancé, thrice-married Steve, as a wrong ’un from the start, with his Florida tan, honed physique and whipped-cream hairstyle. As soon as Karen is asleep, he is coming on hard to Jean, aged 14. “She said she was 15,” he wails, in less than persuasive self-justification.

Meanwhile, Bill is also leaving Barbara for a much younger girl, one of his students — or “porking Pippi Longstocking”, as Barbara puts it. Violet states with evident relish that all older women are ugly, and here is the related fact that all men, all straight men, really, really fancy teenage girls. It’s just that some of them are decent enough to do nothing about it.

There is one glaring fault: in the anaemic characterisation of the home help, Johnna. She’s a Cheyenne, played with perfect sweetness by Kimberly Guerrero, but amid all these dysfunctional, screaming, drunken palefaces, she alone remains implausibly poised and serene, without fault, regularly retreating to her humble attic bedroom to sit in the lotus position, reading a book. She can’t have any humanising faults, it seems, because she’s “ethnic”.

Todd Rosenthal’s set is an ingenious life-size house, opened up like a dolls’ house, and beyond the front porch there’s a powerful sense of the lone and level plains stretching far away. The “Osage” of the title are a Native American tribe, and there’s an eerie feeling that these white Americans are still only recent settlers. For barely three or four generations, they have been stuck out here, 90 in the midsummer shade, in the midst of this “flat, hot nothing”. No wonder the younger generation flee and shift about so rootlessly between Colorado, Florida, New York.

An unconvincing speech near the end tries to suggest that this collapsed family is a microcosm of the wider American family, demoralised and wrecked by the Bush years and the invasion of Iraq — a suggestion emphasised in a peculiarly self-lacerating programme note from the director, Anna D Shapiro. There is, however, “still a chance for us to be saved”. She means by the advent of St Barack, of course. Yet this play is quintessentially personal, not political, and all the more involving and permanent for its close-up, domestic tragicomedy and truthfulness.

Tony Hancock said that the world is “both funny and sad, which seem to me to be the two basic ingredients of good comedy”. This is very sad, very funny, very honest comedy indeed.

August: Osage County

Lyttelton, National, SE1

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