Our Town becomes Our House in the National’s latest hit play, by Tracy Letts. August is a drama of household dysfunction, drawn from a pure American vein, couched in the lilting old-timey manner of the Plains (“not the Mid-West . . . the Plains: a spiritual affliction, like the Blues.”), and set in a time and place so stinking hot that tropical pets die of heat exhaustion: Pawhuska, Oklahoma.

The programme notes suggest I should have read into this some allegory for a troubled America. But I didn’t.

“My wife takes pills and I drink. That’s the bargain we’ve struck.” Beverley Weston is an ageing, bourbon-drinking poet, “the patriarch”. His life is a slow blur – a smudge? – of Jim Beam, denim and books. What more could a man want? Well, something. Having set the domestic scene, Bev kills himself.

Cue comings and goings of Bev’s three daughters, their assorted partners and progeny. The daughters talk through their secrets and lives, and “some people get antagonized by the truth”. Best among these are Barbara (Amy Morton) and her beleaguered-but-philandering husband Bill (Jeff Perry). The show is crowned, though, by a magnificent performance from Deanna Dunagan (pictured) as Bev’s chaotic wife, Violet, with her mouth cancer, drug-addiction, and the voice (and charm) of a rusty gate.

Despite its heavy theme – to let life wash over you or to armour yourself and fight? – this long play doesn’t flag once. Moreover, it is very, very funny – though few of the 50-some classic lines could be quoted here. And the open-dolls’-house staging (Todd Rosenthal) suits the Steppenwolf ensemble’s talent for portraying intimacy.

It’s unclear how far we should sympathise with Violet (weirdly – distastefully, even – the website has a game inviting you to “help crazed Violet get her fix”), and the play is frankly a little woman-heavy. Hearing a gaggle of middle-aged ladies swearing like Michael Madsen and John Travolta is very refreshing; but I’d like to have seen more of the men, Beverley especially.

And though it takes balls to open a play with a five-minute monologue on poetry, however beautiful, there is also perhaps a tad too much literary referencing (Eliot is unnecessarily prominent). The dud lines – only a handful in three-and-a-half hours, mind – sounded suspiciously like the titles of poems Letts hasn’t found time to write.

But these are small slips, on minor points. August: Osage County is, if not an unequivocal, five-star show, then easily a four-and-a-half. Until January 21. Tickets: 0207 452 3000 (www.nationaltheatre.org.uk)