A card-carrying, self-described curmudgeon, Stegner (the fictional Sports Car Menopause, 1977; etc.) finds plenty to grouse about as he caroms through the deserts and forests, the canyons and peaks west of the Mississippi. First, there's the Bureau of Land Management, the lackadaisical (when it comes to wilderness preservation) custodian of some 247 million acres of public lands. Then there are the sullen, self-satisfied students of environmental studies whose idea of ""roughing it"" is going without tofu and alfalfa sprouts during a field trip down Utah's San Juan River. And then there are the yuppies who, having discovered the Idaho backwoods, proceed to transform it into a Ralph Lauren world of chaparral chic. The list goes on and on. Fortunately, however, Stegner airs his complaints with a combination of levelheadedness and wit that is both convincing and immensely appealing. An avid preservationist, the author has a long history of environmental concern--and, here, he also has his facts and figures at hand and uses them to buttress his arguments. If these details are occasionally repeated from section to section, it is perhaps the inevitable result of many of them having first appeared in such diverse publications as The Atlantic Monthly, Wilderness, and The North Dakota Review. Stegner, though, refuses to allow his more serious concerns to outweigh the obvious pleasure he takes in visiting this country's rapidly dwindling wilderness areas--and in coming up with the snappy retort. One of the most effective pieces here concerns a journey along the upper Missouri River. Drawing on the well-known 1804-05 journals of Lewis and Clark, and the more obscure reminiscences of Prince Maximilian and Karl Bodmer that date from 1833, Stegner lends weight and perspective to his own memorable descriptions of the changing face of the river. The interest here begins to wane when, late in the book, the author recounts his fairly predictable adventures as an innocent caught in the complexities of farm life. But the problem is a minor one: for most of its pages, this is a chuckle-filled account of a life of purpose and commitment.