A classic from the moment it was published, Annie Proulx's short story deserves all the acclaim it gets, writes Eileen Battersby

Life never tended to offer all that much to "drop-out country boys with no prospects", the sort of misfit drifters Jack Twist and Ennis del Mar, the central characters in Annie Proulx's Brokeback Mountain, appear destined to become.

First published in the New Yorker magazine in 1997, Brokeback Mountain caused quite a stir. Its length surprised readers. Published in its entirety, it took up most of the issue it appeared in. As well as being very long for a magazine short story, it was also recognised as outstanding, and a further achievement for its author, Annie Proulx, who had already won most of the major literary prizes going including the Pulitzer Prize and the National Book Award. There was also the question of its theme: cowboys in love. The critical response was immediate, here was a definitive American short story and one of the finest US stories ever written set to take its place in the national canon.

Proulx's British publishers, 4th Estate, published Brokeback Mountain in a solo, 57-page edition in October 1998, eight months in advance of Close Range, her second collection, in which it appears - and dominates.

Now Brokeback Mountain moves a step further; as a great American short story set to become a great American movie. Proulx is a tough, relentless visionary with a firm belief in brutal realism, and realism seldom comes harder or more profoundly than it does in this story and in Ang Lee's screen version. As cinema goers will shortly see, the film is set to match the superb versions of Russell Banks's magnificent novels Affliction and The Sweet Hereafter, both well served by cinema.

Stern, ironic and unsentimental, but not without compassion, Proulx has taken an American icon of mythic dimensions, the cowboy, and placed him not in the centre of a heroic shoot-out or a romance, but at the mercy of a love so doomed and so real that suddenly it becomes clear that real passion is the ultimate human experience. Her rugged, physical art lies in her daring, often risky use of language.

There's no doubting that Jack and Ennis are losers, if opposites by temperament. They first meet as teenagers, and "neither of them was 20" when they end up working together on a lonely, slightly dodgy undertaking - minding sheep grazing illegally on a bleak Wyoming mountainside. All very underhand; one of the youths is expected to keep camp and fetch supplies, while the other minds the flock, keeping the coyotes at bay and most especially, avoiding the forest service rangers. "Sleep with the sheep, hundred percent" orders their employers, "no fire, don't leave no sign."

Ennis had wanted to be a college sophomore, but even high school eludes him when his truck breaks down and the expense forces him to turn to ranch work. We know he is big and strong, capable of violence, a bit innocent and diffident. His "heart shot" passivity causes his romantic side to invariably bow to the more prosaic. "If you can't fix it you got to stand it." Jack Twist has a different attitude, a failed rodeo rider, he is restless, hungry and sustained by a terrifying need which both drives and destroys him.

Characterisation is all for Proulx, who draws on her raw, authentic use of vernacular speech at its most jagged. Here is the articulation of the inarticulate, the despair and desperation of desire, loss and regret. Not for nothing is Jack Twist dubbed "Jack Nasty" by Ennis's wife. If Ang Lee can capture the wry tone and essential detachment of this beautiful story, he will have arrived at its essence.

It begins in the 1960s but it could be anytime. Ennis and Jack are as out of time as they are out of place. Ennis is an orphan, his parents were killed when driving off "the only curve on Dead Horse Road". Jack is the son of a brutal father who had been a rodeo rider himself but never shared his riding secrets with his son and never bothered coming to see Jack ride. So the scene is well set.

In their solitude they find companionship - and far more than either of them bargained for. Their boss, however, has been observing their activities, "I know what you've been getting up to on that mountain." The pair part awkwardly. Four years pass before they see each other again. Ennis is married with two daughters. Their meeting is observed by Ennis's wife: "She had seen what she had seen." Time passes and there are more furtive meetings. Ultimately Proulx defines their shared tragedy: "They were no longer young men with all of it before them." Brokeback Mountain is a profound study of love, it is also a magnificent short story which travels triumphant to the screen.