IN MONTANA, Ivan Doig tells us, the mountains are the calendar. When the snow line shrinks along the peaks, deer return to the high ground and youngsters work on their saddles lengthening the stirrups to account for the past winter's growth. So it was the fateful summer of 1939, the time of Doig's second novel, English Creek, the splendid story of a boy's coming of age in the American West.

June that year came in wet, and was remembered long after for its green high-grass by English Creek's narrator, 14-year- old Jick McCaskill. As the novel opens, Jick is much puzzled by the behavior of his older brother, 18-year-old Alec, who has fallen in love with a town girl. Their father, a U.S. forest ranger, oversees part of Two Medicine National Forest, a fictitious wilderness bordering Glacier National Park on the south. Their mother, a former school teacher, carefully watches over her menfolk and the household expenses. This is a family "scraping along better than many" after years of hard times and drought.

The McCaskills live where the great plains reach the east face of the Rockies, in what they call the Two Medicine country, and we quickly learn what a Montanan means by "country": the terrain all the horizons around, a landscape bounded by the breathtaking grandeur and hundred-mile vistas of the Continental Divide.

When Alec proclaims his intent to marry the curvaceous Leona, instead of attending college, his parents object. Alec rebels and leaves home to be a cowpoke on the Double W Ranch. Unexpectedly, Jick makes a pack trip into the mountains with the seedy Stanley Meixell, an alcoholic ex-ranger with a mysterious background. The novel closes at summer's end, on Labor Day weekend, as war breaks out in Europe. There is an epilogue and Jick, now threescore years, reveals how that summer changed and shattered his family forever, despite boundless love. In that time, Jick learned, and would continue to learn, the terrible lesson of growing older: "The past is a taker, not a giver."

What sustains this unexceptional plot is some very exceptional writing. Indeed this is not a conventional western novel at all. The high points are muted: there is a Fourth of July picnic, a square dance, a rodeo. They are all treated satirically. The forest fire at the novel's climax is described through the eyes of the firefighters' cooks -- a really brilliant narrative tactic. In between we learn quite a lot about raising sheep, making hay, digging a new pit for an outhouse, naming horses, and much else:

"My earliest memory of this brother of mine was the time, I must have been four and him eight, when he took me into the pasture where the ranger station's saddle horses were grazing and said, 'Here's how you mooch them, Jick.' He eased over to the nearest horse, waited until it put its head down to eat grass, then straddled its neck. When the horse raised its head Alec was lifted, and slid down the neck into place on its back and simultaneously gripped the mane to hang on and steer by. 'Now you mooch that mare,' Alec called to me and I went beside the big chomping animal and flung my right leg over as he had, and was elevated into being a bareback rider the same as my brother."

ADMIRERS OF Doig's beautiful memoir of Montana, This House of Sky, and his adventurous first novel, The Sea Runners, will have high expectations for English Creek. They will not be disappointed. Doig seems to be one of those enviable writers whose every book is better than the previous one. The new novel is full of good writing and the sweat and tears and laughter of hardworking plain people -- people whose lives are shaped by a land which as it grows more scenic becomes more hostile to human habitation, the incomparable Big Sky country of western Montana.

The McCaskills' world is the vanished one of prewar rural West, evidently a place where the brooks are always full of trout and the lodgepole pines are as straight as the local morality. But rural and western do not mean simple, and in fact English Creek makes fun of the rustic trappings we associate with western life: when young Alec shows up in a rodeo outfit which includes a red bandana around his neck, his father mercilessly asks, "What, is your Adam's apple cold?" It is the heroic oldtimers whom Doig honors, the first ranchers and the surviving cowboys who can ride a horse but not drive a car, true cowboys like Toussaint Rennie, out of place even in 1939 but who can dimly remember the roundup of 1882 when the cowmen fanned their crews "north to the Canadian line and brought in a hundred thousand head" and a great buffalo hunt when the prairie "looked burnt, so dak with buffalo, the herd pinned into place by the plains tribes."

Commonly compared with Paul Horgan and Wallace Stegner, other writers of the American West with distinctive styles, Doig seems something else. He is more virile than Horgan and less romantic than Stegner. A truer comparison might be with Robert Louis Stevenson because of Doig's magical welding of history with fiction, of adventure with everyday life, of legend with lore. English Creek, just like Kidnapped, can be read by both old and young with equal pleasure, fascination and excitement. It just might become -- one must be cautious -- something of a western classic.

It surely will become a classic for those readers who know what Doig means when he writes, "I cannot even safely say what the weather was, one of those brockled late afternoons under the Rockies when tag ends of storm cling in the mountains and the sun is reaching through wherever it can between the cloud piles."