Meryl Streep plays a shrieking matriarch in this overwrought and overlong movie based on Tracy Letts' Pulitzer Prize winning play about family dysfunction. Bring a good book.

Like the opening sequence of Jonathan Franzen's debut novel The Corrections, a kind of silent alarm sounds through much of this bespoke soap opera from director John Wells. It rings unheard until it comes to full, ear-splitting volume and a pained pretence of family solidarity finally breaks down and messy truths are revealed.

Of course, August: Osage County is perfect Oscar bait for a blinkered Academy who most likely think that this ensemble of "real" actors and the story of familial dysfunction is a proper, grown-up film heavy with a great aching sadness about how, you know, life can be a real downer sometimes.

Meryl Streep plays matriarch Violet Weston. She lives in a sprawling old house stuck out on the endless plains of Oklahoma which has, like her marriage, long gone to seed. Her professorial husband Berverly (an elegantly-grizzled Sam Shepard) intones that they have come to an arrangement - he drinks; she gobbles a cocktail of uppers, downers and medication for the mouth cancer she is battling.

Violet's illness is a none too subtle metaphor. When not deranged on pharmaceuticals, her bitterness emerges with surgical cruelty as she carves up all around her with a real verbal dexterity. When Beverly dies in a boating accident, she gathers her children - the tough, unemotional Barbara (Julia Roberts), the comically selfish Karen (Juliette Lewis), and the patient and lovely Ivy (Julianne Nicholson).

Also along for the ride are Violet's sister Minnie Fae Aiken (a hilarious Margo Martindale), her husband Charles (the great Chris Cooper), and their son, Little Charles, who is played with agonised diffidence by Benedict Cumberbatch.

The stage (and the film rarely escapes its theatrical origins) is set for a protracted descent into grandiose inter-generational warfare. Streep is the malevolent centre of all things as volcanic Violet and her performance is, indeed, magnificent in a movie that limps from shrill showdown to shrill showdown.

The Weston clan prod each other's scars in the still, searing heat of the American mid-west but this story of dark family revelation would be laughed out of an EastEnders script conference, a consequence, perhaps, of the director's background on shows like The West Wing, the US version of Shameless, and ER.

Wise and craggy old Sam Shepard is given to quoting TS Eliot's line "life is very long" at the start of August: Osage County. That may well be, but it's still too short to find the time or energy to watch this nagging migraine of a movie.

Alan Corr