Picking his time to cut the rope

Seventeen years ago, Joe Simpson and his friend Simon Yates embarked upon what turned into the adventure of their lives, their defining moment both as men and as climbers. High in the Cordillera Huayhuash, in the Peruvian Andes, they set their sights on climbing the hitherto unscaled west face of Siula Grande.

On their way down, the summit successfully bagged, Simpson fell and broke a leg. Yates, to save his own life - and according to the unwritten mountaineering code - cut the rope between them. Simpson's account of the journey - and of his own miraculous crawl back to the safety of base camp - became Touching the Void, now widely acknowledged as a classic of mountaineering literature, to stand alongside such works as David Craig's Native Stones or Heinrich Harrer's The White Spider. And Simpson - buoyed by the success of the book - went on to become an established mountaineering author.

Now, though, it looks as if his writing might be coming to an end. The Beckoning Silence, his latest, has a ring of finality about it. "The attrition of friends over the years had begun to eat away at my confidence, at my nerve," he writes. For the first time in his life, nearing 40, he was finding it "increasingly difficult to psych myself up for this climbing game".

It was only after some persuasion from his literary agent that he sat down and began to write again. What has resulted feels valedictory: a long, bittersweet farewell to the mountains he has loved and which have given his life much of its meaning.

What comes through strongest is the paradox of climbing: its danger, and yet its attraction. A single photograph - included in the plate section - encapsulates this beautifully. Four climbers - Harrer, Fritz Kasparek, Anderl Heckmair and Ludwig Vorg - laugh euphorically, arms around each others' shoulders. The year is 1938, and they have just completed the first ascent of the fearsome north face of the Eiger in Switzerland. Just to one side are the awestruck faces of two young boys, staring open-mouthed, as if in adoration.

The ascent they have just witnessed, after all, is one of the world's legendary climbs: more than 60 men have died attempting it.

For much of Simpson's life, such danger was "where you defined yourself, balanced tenuously between life and death". But then, almost destroyed by a rockfall in the Bolivian mountains in 1998, the truth dawns. "I no longer loved the mountains."

With the words of Canadian mountain poet Syd Marty ringing in his ears - "Men fall off mountains because/ they have no business being there" - he decides instead to take up paragliding. And, for a while, this suffices. "I could fly. It seemed pretty damned special." Gradually, however, he returns to the mountains and finally, unable to refuse an invitation from a friend to attempt the north face of the Eiger, he finds himself in Switzerland.

Such is the sheer difficulty of the almost sheer north face that it has become its own legend, and Simpson brilliantly splices his own preparations with the stories of those who have gone before. He also, somehow, manages to write with a winning black humour: a "peeler" or "lob", he explains, is a "scary but survivable short fall"; a "zipper" is when all your gear "rips out". "So 'bombing off ', an uncontrolled free fall, can rapidly escalate into a 'screamer', particularly if zipping occurs."

All levity disappears, however, when he and his climbing partner - halfway up the north face - are hit by a thunderstorm. During the deluge, he hears a strange, muffled sound: only later does he discover that this was the noise of the two climbers above him falling to their deaths.