By Aron Ralston. Atria. 354 pp. $26

Could you cut off your own arm if it were the only way to save yourself? Aron Ralston made headlines by doing just that. This account of how he was trapped in an isolated Utah canyon for six days, and how he methodically went about extricating himself, is more than just another tale about those who head into the wilderness seeking their bliss and get lost.

A former Intel engineer, Ralston identifies with Chris McCandless, the introspective seeker of Jon Krakauer's Into the Wild, which raised true adventure to a new level -- and to the bestseller charts. But McCandless was a loner and hobo who abandoned his possessions, burned his money and died of starvation in Alaska while acting out what Krakauer believed was a complicated rebellion against his father. By contrast, Ralston initially comes across as a cocky adrenaline junkie, loving son and punctual employee who nevertheless courts danger.

Born in 1975, Ralston was scared of snow when his parents first moved from Indiana to Colorado. But he adapted spectacularly. While still in his teens he was skiing, climbing, rafting and planning to climb in winter all 59 of Colorado's Fourteeners -- peaks over 14,000 feet high. He graduated from college with a double major in mechanical engineering and French, as well as a minor in piano performance, although strangely he says nothing of his musical ability or the accident's effect on it.

His resume was filled with close encounters. A bear stalked him in Grand Teton National Park. He nearly drowned in the Grand Canyon. He was trapped high on a mountain in a snowstorm. While he was back-country skiing, his "cavalier attitude" led him to choose a route that triggered an avalanche. It nearly buried him and two friends -- both of whom, he admits, have refused to talk to him since.

"Rather than regret those choices," he writes, "I swore to myself that I would learn from their consequences. Most simply, I came to understand that my attitudes were not intrinsically safe." As we know now, he didn't learn. It is as exasperating to read his confessions of hotdogging and recklessness as it is inspiring to see how logical he was once he got stuck.

His fateful weekend begins with climbing a major peak in Colorado, then speeding off in his jeep to mountain bike to a remote trailhead for what he expects will be a fun day of slithering through sandstone labyrinths, his headphones blaring Phish music. He takes almost no food and very little water. Nor does he tell anyone where he is headed. Then he accidentally jiggles loose an enormous rock that wedges his arm against a canyon wall. Realizing quickly that he might be facing death, he videotapes heartfelt goodbyes, including instructions on how to locate his IRA portfolio.

Warding off morbid thoughts, he launches ingenious self-rescue maneuvers. He tries chipping away pieces of the boulder. When that doesn't work, he rigs a pulley system in a futile effort to move it. As he describes, in excruciating detail, hour upon harrowing hour of dehydration and then delirium, we learn that he actually tried sawing off his limb early on, but failed. The moment that he figures out he must break the bones in his arm first so he can cut through soft tissue sounds horrible, yet Ralston feels triumphant.

If Aron Ralston had been just an accident waiting to happen, why should we care about him? First, because there are thousands of potential victims like him. Colorado officials estimate that a half-million people climbed at least one Fourteener last year. Adrenaline fever is contagious; on occasion it is deadly. Heedless wilderness tourists routinely wander off without so much as a water bottle. And anyone who has hiked solo has probably taken a wrong turn or a scary fall. Has it ever dawned on us what the consequences might be should we break a leg or get caught in a flash flood?

We also care because Ralston writes very well. His thoughts ricochet from anger to anguish to acceptance. He recounts the joy of risk, and he takes full responsibility: "The boulder did what it was there to do. Boulders fall. . . . You did this, Aron. . . . You chose . . . to do this descent into the slot canyon by yourself. . . . You created this accident. . . . You have been heading for this situation for a long time." His recital even takes on a weird humor as he notes that his self-amputation is more successful than his botched dissection of a sheep's eyeball in a ninth-grade science class.

Once he frees himself, the story accelerates into a riveting drama as he rappels one-handed down a cliff and staggers through rough terrain for miles, blood leaking through his tourniquet as he tries to find help. Aron Ralston went to Utah as just another rock jock; he emerges as a Gen X action hero. *

Grace Lichtenstein, who formerly covered the Rocky Mountain West for the New York Times, is an avid skier, hiker and cyclist.

Aron Ralston had to sever his right arm to free himself in Blue John Canyon.