'I am reborn. This is my dawn': The remarkable life and lonely death of Christopher McCandless

When, in September 1992, a hunter came across the remains of a young man in the Alaskan backcountry, there was little to suggest that the emaciated corpse would be anything more than a footnote in the annals of America's wilderness state: one of the underprepared loners who come to the state to prove themselves against its forbidding terrain and climate, and pay dearly for their inexperience. But if Christopher McCandless had arrived in the state as an unknown 24-year-old, in death he was soon to become one of the more famous adventurers to disappear into the depths of Alaska's interior.

Within a few months, local coverage of the fate of McCandless attracted the national press, and in 1996 the writer Jon Krakauer expanded a long magazine article he had written. In the resulting book, Into the Wild, Krakauer trod the footsteps of McCandless as he gave his savings to charity, turned his back on his comfortable upbringing on the outskirts of Washington DC, burned the cash in his wallet, wandered about the American West, and sloughed off the trappings of civilised society – all the better to live up to the persona he coined for himself, "Alexander Supertramp".

Krakauer traced his quarry all the way to the scene of his death: a remote, abandoned bus on the wild, north-eastern edge of Denali National Park in Alaska. With the journal and photo films recovered from McCandless's belongings, he pieced together the final few months of his life: the elation at fending for himself and communing with nature, and the encroaching despair as McCandless realised he had trapped himself in his idyll, and was starving to death.

McCandless is thought to have succumbed in mid-August 1992, and Krakauer didn't just detail the exploits of a foolhardy young man, but turned him into a figure as romantic and enigmatic as any in America's frontier history. Into the Wild spent two years on the New York Times Best Sellers list, was translated into 28 languages and eventually, in 2007, became an Oscar-nominated film directed by Sean Penn. Over that time, countless pilgrimages have been made by acolytes of the McCandless creed to his final resting place, the "Magic Bus" – yet, as Walt McCandless explains, the appetite for his son's story appears insatiable.

"There are a huge number of people who've contacted us [over the years]," says Walt, 75, a former Nasa engineer. "I don't truly understand it. I'm amazed it's so continuous. There's a part of everybody that looks at what Chris k did and thinks, 'That's something I'd like to do.'" In part response, the McCandless family have decided to publish Back to the Wild, which, using more than 200 of their son's photographs, chronologically arranged and carefully annotated with his writings, tells the story of his final two years, including his fateful trip to Alaska.

McCandless broke off contact with his family over this period, but he wrote letters and postcards to friends he met while travelling and made journal entries emphatically justifying his choices ("I am reborn. This is my dawn. Real life has just begun.") Throughout, he smiles from the photos as if in disbelief at the wide open spaces before him.

Despite the enormous potential audience for the book, Back to the Wild came into being only when Walt was advised by a lawyer to catalogue the photography for copyright purposes – at which point he had had no thought of publishing them. But, due to a procedural error, he had to recatalogue the images, and it was this that led to the idea of the book. "The first time was an act of labour," he recalls. "The second time, the light flashed on."

Moroever, Walt found the "forensic" cataloguing process led him to a deeper understanding of his son's quest: "I think I know him better, and it's been a positive experience. But my wife Billie has a hard time looking at the pictures." The last time Walt or any of Chris's close family heard from him was around his graduation from college in 1990. "Then communication stopped," says Walt. "Why? I have thought about this a lot and can only conclude that he knew that a major effort would ensue to find him if communication occurred. We did make an enduring attempt to track him via a hired investigator."

The exultant, determined young man on the pages of Back to the Wild is far from unfamiliar to Walt, who recalls a teenager enraged by apartheid and inequality in general, and who once housed a homeless person in the family's Airstream caravan. "For years we hiked in the Appalachians, and on [Chris's] last journey we were on our way down a mountain when we heard this clank, clank, clank coming down the trail. A couple of kids came round the corner – they were about 19, 20; Chris was 16. All they had were rolled-up blankets and a cast-iron skillet. We had a super-lightweight stove. Chris turned to me and said, 'That's really the way to do it.'"

The McCandlesses now run a charitable foundation in their son's name, and distribute a substantial amount annually. What is the legacy of Chris's journey? "Hopefully it's to enable people to look at what to do with their lives and take some steps in that direction. Not many people are able to do what Chris did – thankfully, in many ways. It's high risk."

A team of family and friends has assisted in publishing Back to the Wild, and in March Walt took them to Alaska to visit the bus. "When we first visited the bus [after Chris's death], we decided to leave his effects there. But they're now gone. The book didn't change things much, but after the film, people took stuff – instruments [from the bus] were offered on eBay." Nevertheless, says Walt, "The bus is still proud, growing into the landscape."

'Back to the Wild' is published by Twin Star Press, and is available from backtothewildbook.org