BOOK REVIEW: NONFICTION : A Powerful Story of Self-Discovery, Survival in the Wild : BACK FROM TUICHI: The Harrowing Life-and-Death Story of Survival in the Amazon Rainforest, <i> by Yossi Ghinsberg</i> ; Random House, $22, 239 pages

All great stories of survival start out as something else--an airplane fight over the Andes, a cruise around the world by sailboat, or, in the case of Yossi Ghinsberg’s “Back From Tuichi,” an expedition into the Amazon rain forest in search of gold, wild animals and natives.

Like many young Israelis, Ghinsberg set off in search of adventure after completing his military service, and he joined the other young vagabonds--or mochileros --who wandered the byways and backwaters of South America. The symbol of their freedom, as Ghinsberg explains, was the backpack, or mochila .

“Every nomad knows the feeling,” writes Ghinsberg. “The idea is to carry everything on your back, forget your troubles, let tomorrow take care of itself.”

Ghinsberg’s journey into the rain forest, as we learn, was the idea of an Austrian expatriate named Karl, a colorful but faintly sinister character who attached himself to Yossi and his friends in La Paz, and offered to serve as their guide on what he promised would be a particularly memorable trip by raft down the Tuichi River. Karl was right, as we learn in “Back From Tuichi,” but for the wrong reasons.

As it turns out, Karl is the central figure in the mystery that unfolds in Ghinsberg’s book. Was Karl a geologist, as he sometimes claimed to be? A gold and uranium prospector? Or an international fugitive with a price on his head? Did he really have an uncle who was a Nazi war criminal in hiding on a distant rancho? And exactly why did Karl tantalize Ghinsberg and his friends with half-truths and outright lies about what they would find in the rain forest?

Ghinsberg’s account of the expedition is as enchanting to us as Karl’s stories must have been to Yossi and his traveling companions, an American named Kevin and a Swiss named Marcus. He shows himself to be a gifted storyteller as he describes the treacherous rapids of the Tuichi River, the snake-infested thickets of the rain forest, the forbidding cliffs that lay between the young adventurers and the village where they intended to catch a bush flight back to La Paz.

Almost immediately, the expedition goes wrong in subtle ways. Karl’s lies begin to reveal themselves; the young men fall out with each other; the rain forest exacts a far harsher price than they had expected to pay. In its darkest passages, “Back From Tuichi” is a Conradian tale of men at odds with themselves and each other in the very heart of darkness.

At the moment of greatest crisis, Ghinsberg finds himself utterly alone in the mal paso of the Tuichi River, an impassable canyon where white water crushes the improvised raft that was to carry the young men to safety. And now the real adventure begins: Can Ghinsberg survive--alone, unarmed, untrained and poorly provisioned--in the Amazon rain forest?

“You’re a man of action,” Ghinsberg tells himself in a phrase that becomes his mantra during his long, lonely ordeal in the rain forest. “Don’t cry. Don’t break now.”

What allowed Ghinsberg to survive alone in the wilderness? As in other classics of the literature of survival, Ghinsberg describes the blend of physical courage, practical knowledge and quiet spirituality that allows him to survive the deadliest threats of the wilderness.

Some of the most fascinating passages in “Back From Tuichi” describe the improvised jungle craft that allowed the intrepid Ghinsberg to prevail against hunger and injury, leeches and fire ants, jaguars and wild boars, high water and thunderstorms. And yet Ghinsberg’s bravery and ingenuity are not the only secrets of his survival. Ghinsberg placed his faith in a little book that a beloved uncle has bestowed upon him, a talisman that saves his life and his sanity.

“The sun shone over me,” he writes of a sublime moment of respite during the lonely jungle trek. “Every now and then I put another ripe tamarind in my mouth and greedily sucked the sweet flesh from the pits. Wild beauty surrounded me . . . alone in the heart of the wilderness along with whoever was watching over me.”

I will not reveal exactly how Ghinsberg’s ordeal turned out, but the end of his sojourn in the rain forest is not the end of the adventure--or of the mystery. We learn Kevin’s fate, but Ghinsberg leaves us only with an intriguing bit of speculation about what became of Karl and Marcus--an explanation that only deepens the ominous shadows behind Ghinsberg’s story of survival.

“What I’m doing here in South America is looking for the extraordinary,” Ghinsberg wrote his brother before his journey. “Mystical religious ceremonies, pagan rites. . . . Unusual people, places that have their special atmosphere, new friends, all those things.”

As we discover in “Back From Tuichi,” Ghinsberg found all of the exotic experiences in the rain forest of South America. But, at the end of his remarkable book, we understand that he happened upon something even more extraordinary--and he found it in himself.