RIDGEFIELD — If there is one piece of live theater you get to see all year, make it Ridgefield Theater Barn’s August: Osage County.

When Tracy Letts’ dark tragic-comedy premiered on Broadway in 2008, it swept all the prizes, garnering in addition to the Pulitzer for that year, five Tony Awards, three Drama Desk Awards, three Outer Critics Circle Awards, and the NY Drama Critics Circle Award for Best Play.

And a woman in the Theater Barn’s lobby was heard to remark the other night, “I saw the original show in New York … and this production’s better!”

Letts acknowledges being influenced by Tennessee Williams, but this three hour, three act, highly realistic study of a family is more suggestive of a contemporary Long Day’s Journey Into Night —if Eugene O’Neill had gotten some input from George Carlin or Dennis Leary.

Set in the Osage County, Oklahoma home where family patriarch Beverly Weston and his wife Violet are disintegrating separately into alcoholism and drug addiction, the play follows the efforts of their three daughters to cope when Beverly unexpectedly disappears. Barbara, the oldest sister, arrives from Denver with her husband, Bill, and their rebellious 14-year-old, Jean.

Karen, the youngest, breezes in from Florida with her new fiancé Steve, while Ivy, the middle sister, who has remained in their hometown, working in the college library, endures endless taunts from her mother over her inability to find a man.

They are joined by Violet’s sister, Mattie Fae, and her husband, the sweet-tempered Charlie, and finally, all of them are tended to by Johnna Monevata, the young Cheyenne Indian woman whom Beverly hired as a caretaker for Violet, and whose duties have expanded to cooking and cleaning for everyone.

Johnna serves as a kind of chorus to the tragedy, observing the destructive dynamics of this dysfunctional clan, spending much of the play lying motionless on her attic cot, reading T.S. Eliot’s The Wasteland.

Eliot is clearly meant to be a presence: his portrait dominates Beverly’s study, and it was Beverly who gave Johnna the book. Beverly had been a poet, publishing several highly regarded volumes of verse in his youth, as well as teaching literature at the local college. It has been many years since he produced any work, however. Instead, he spends his time systematically drinking through the day, while his wife floats in and out of a demented fog, depending on how many different pills she has ingested.

Under the masterful direction of David Bass, the 13 members of the cast in Ridgefield are uniformly superb, so that you never feel you are watching actors perform. Rather, in the intimate settings of the Theater Barn, real people are grappling with a tangle of emotions: resentments, jealousies, hidden secrets and fragile hopes.

It’s hard to single out any one of them because they are all so good. In a brief role, Manny Lieberman displays a weary but kindly courtliness as he interviews Johnna, remembering her father who sold fruit from a truck (along with illegal fireworks) and nodding understandingly as she explains how she had to drop her nursing studies when her parents died.

Jasmin Barbosa makes the most of Johnna’s part, hiding her own pain behind a surface cheerfulness and energetic desire to please. In contrast to the Westons, her family had been a loving one. She wears her identity in a leather pouch necklace, so that she will always know who she is, wisdom that enables her to see these people with empathy and insight.

Flori Doyle has the central role of Violet, the damaged matriarch, who alternates being what her children see as a loony tunes, with  moments of shrewd perception. As she assures the daughters, nothing gets by her. She is aware of every painful secret, every betrayal, and everyone else’s darkest intentions, and she is happy to reveal them all, skewering them all with taunts and insinuations, before she dissolves into tears of panic and helplessness.

Her counterpart is Kelly Kirby as Barbara, a woman as strong as her mother, intent on controlling her world and seething with rage and frustration because she can’t.

As her husband Bill, Bruce Tredwell is the easygoing Midwesterner, brimming with kindness and sympathy, while steadfastly ignoring her pain over the fact that he has left her for a young student.

As the teenager who reacts to her father’s infidelity by experimenting with drugs and sexual adventurism, Livi Woods is totally believable. If they have seen the show, her own parents must be shaken by the calm and sullen assurance with which she positively drips alienation.

With her Diane Keaton looks, Rosemary Howard makes Ivy a mixture of hurt feelings and long suffering patience, keeping her own secret hidden, against the prying inquiries of her family.

Maria De Vries turns the youngest sister, Karen, into a pretty airhead, happily spouting new age nonsense in the face of her sisters’ mounting astonishment and scorn, while Timothy Huebenthal conveys the sinister dimensions of smiling Steve that Karen seems oblivious to — from his unsavory involvement with mercenary contractors (so that he can “get as rich as Cheney”) to his predatory attempts to seduce the 14-year-old, plying her with extra strong weed and teaching her grown-up games.

Laurel Lettieri and Jon Barb as Mattie Fae and Charlie — Violet’s insufferable sister and well-meaning brother-in-law — provide important insights into the past, explaining the emotional pathology that has so crippled this family.

Finally in two smaller roles, Chris Luongo as Mattie Fae and Charlies’ ne’er-do-well son, and Alexis M. Vournazos as a local sheriff who comes with bad news, keep up the high standards.

What is so impressive about both the play itself and these performances, is that however awfully they behave, we still care about these people. As Karen says, when confronted with Steve’s pederasty, “He’s a human being!” They are all human beings, however damaged, hurtful, or self-absorbed, and our attention is absolutely riveted, through the startling, disturbing, and totally unexpected ending.

(Performances continues weekends until October 5 at Ridgefield Theater Barn, 37 Halpin Lane in Ridgefield. Note, however, that there are no performances this Friday and Saturday, September 13-14, in observance of Yom Kippur.

Tickets are $20 and $24, and are available online at RidgefieldTheaterBarn.org. Tickets and additional information is also available through the theater’s box office, at 203-431-9850.)