Not since the 1891 English premiere of Ibsen’s Ghosts, with its cryptic talk of syphilis, incest and assisted suicide, has there been a family reunion play more crowded with sensational incident than Tracy Letts’s August: Osage County.

Invoking the spirit of O’Neill, Albee and Shepard a family comes together in Oklahoma for a father’s funeral and breaks up, choice secrets dragged from the closets of reticence.

Produced by Chicago’s famous Steppenwolf company and decorated with Broadway honours Letts’s play breaks with theatre tradition by interpreting family life as slapstick tragedy, black comedy and steaming hot soap opera all rolled into one.

It’s an extravagant mixture, hard to swallow, despite the bursts of cruel laughter that Letts’s characters so often inspire. Excessive elements of soap opera and abrupt oscillations from high pathos to near farcical comedy in Anna D Shapiro’s superlatively acted production inspire disbelief. We are supposed to see in this American family a microcosm of the country’s moral decline, but the conceit strikes a contrived note.

Designer Todd Rosenthal fills the stage with an imposing three-storey country house, its fourth wall removed to make us enthusiastic voyeurs. The disappearance of Beverly Weston’s septuagenarian, a briefly famous poet deep in the forgetfulness of alcohol, precipitates the return of the family members, whose shares in unhappiness seem unfairly pitched well above the national average and bordering on the preposterous.

If only Letts’s people, forever in flight from reality, ran less true to clichéd form. These characters take to suffering and rancour with malicious though comic enthusiasm. Beverly’s widow, Violet, her cruel tongue part of a mouth affected by cancer, has become hopelessly addicted to uppers but this does not diminish the force of her wit.

Her three daughters have long since succumbed to marital disappointment: Barbara trails along with Bill, her almost separated professorial husband, in love with one of his students and on whom she unleashes a withering scorn. Her daughter teeters on the verge of under-age sex. Forty-year-old Karen, after years of unhappiness, is poised to leave for dream-land and marriage. Plainer Ivy secretly romances a dimmish cousin. The funeral dinner, over which Deanna Dunagan’s magnificent, steely, tottering Violet presides like some vicious bird of prey swooping to peck its victims, serves as catalyst for recriminations and revelations. The family remorselessly falls apart, leaves Violet to isolation. The high-voltage acting, displayed particularly by Amy Morton’s impassioned Barbara, Mariann Mayberry as her silly, self-pitying sister and Rondi Reed, majoring in vulgarity as Violet’s sister, finally lends this torrid vision of the American dream turned living nightmare a memorable strangeness.