Aron Ralston says his mother used to tell him he didn't have enough common sense. But it may be common sense — in the face of seemingly impossible odds — that saved his life 16 months ago.

Ralston experienced instant fame after his right arm became wedged between an 800-pound boulder and a rock wall while climbing in Utah's remote Bluejohn Canyon. After five days of trying everything he could think of, in desperation he cut off much of his arm. Then he rappelled down the canyon and walked seven miles before encountering other hikers and being spotted by a helicopter rescue unit.

Now Ralston has written a book about his ordeal — "Between a Rock and Hard Place." He'll be in Salt Lake City at 7 p.m. Friday to sign copies of his book at The King's English Bookshop, 1511 S. 1500 East.

"I am an introspective person," the 28-year-old engineer said during a telephone interview with the Deseret Morning News. "It's part of my nature.

"Since I was 5, my mom has told me I don't have a lot of common sense, so I try to learn from my experiences. It stems from the analytical side of my personality. It's what made me an engineer, and my high school training in speech and debate also helped me to learn to think on my feet."

Ralston readily admits talking to himself during his five days trapped in the slot canyon. It happened after he quickly drank a third of his water supply — then panicked.

"I said, 'Calm down! You will kill yourself with this behavior.' I didn't panic again until the end — just before I gained my freedom. It was the catalyst to help me realize I could break the bones in my arm. Afterward, I was euphoric."

Ralston demonstrated a rare talent during his predicament — that of coolly analyzing his situation and carefully considering various alternatives. He thinks of himself as a problem-solver, accustomed to "brainstorming, gathering information, prioritizing and executing a solution."

"By the time I executed the amputation, I had made three unsuccessful attempts. Each time I learned something. I learned the capabilities of the blade I had, I learned how severe the pain would be — and that breaking the bone would be the most difficult challenge."

During the fifth night he realized he could die at any moment.