Welcome to Osage County, population: showily deranged. This is one heck of a place. Nobody is able to open his or her mouth without touching on some terrible repressed secret or pondering the festering hatred that poisons the speaker's miserable life. Dinnertime conversations are carried out at a pitch of bitchy intensity that makes the party in Who's Afraid of Virginia Woolf seem like a Teletubbies tea-dance.

We must thank Tracy Letts for cutting his enormous, Pulitzer Prize-winning play down to a manageable two hours. Unfortunately, the editing only serves to concentrate the rampant theatricality. It's not just that life takes place entirely through speeches, mordant anecdotes and grand set-pieces. At least as oppressive is the need to pack every closet with an ossuary's worth of skeletons. By the close, one would not be entirely surprised if – remembering the soap opera in Tootsie – mad matriarch Meryl Streep tore away her make-up to reveal a corseted Dustin Hoffman.

Dragging out one of the most familiar set-ups in literature, Letts invites a troubled clan to return home for the pater familias's funeral. Understandably irked by sharing the planet with such a wretched brood, Beverly Weston (Sam Shepard) looks to have flung himself into a nearby lake. His pill-popping, poison-tongued wife Violet (Streep) – recovering from a clumsily ironic case of mouth cancer – sharpens her canines in preparation.

Violet is not short of fresh meat. One daughter (Julia Roberts) is breaking up with her husband (Ewan McGregor). Another (Juliette Lewis) is engaged to a vulgar perv (Dermot Mulroney). A third (Julianne Nicholson) has drifted into a relationship dubious enough to cause Tennessee Williams or Eugene O'Neil to fan armpits.

Directed (perhaps from another room) with hands-off anonymity by John Wells, August: Osage County is preposterous from chewy beginning to mordant ending. Streep is almost bad. Roberts is almost good. You would, however, have trouble arguing that it's anything less than entertaining. It is often hard to know if one is laughing at intentional jokes or bad writing – I point you to the "Eat your fish!" sequence – but the sheer couch-chewing craziness of the enterprise certainly sets it apart.

Now, it’s time for a quiet lie down.