“Nothing belongs to us any more; they have taken away our clothes, our shoes, even our hair; if we speak, they will not listen to us, and if they listen, they will not understand. They will even take away our name: and if we want to keep it, we will have to find our strength to do so, to manage somehow so that behind the name something of us, of us as we were, still remains.”

So Primo Levi describes the beginning of the process of “the demolition of a man”, the “offence” that Auschwitz inflicted on so many people. “Häftling,” he writes in If This Is a Man, using the German word for prisoner, “I have learned that I am a Häftling. My name is 174517.”

Throughout If This Is a Man, Levi reiterates that survival was mainly a matter of random events, coincidences and fortune. But it also required stubborn resistance. As Levi explains an afterword, he remained “determined to recognise always, even in the darkest days, in my companions and in myself, men, not things.”

Levi holds on to this humanity until the camp is liberated. But he has been hollowed out by hunger, toil and unremitting horror. His sense of self has been undermined by mental and bodily weakness and the moral compromises needed for survival. If This Is a Man finishes with Levi in a kind of perilous limbo. He hasn’t “drowned”, as he terms it, but nor does he show us much about salvation. The last pages are strange and abrupt. The Russians arrive as Levi and a companion – Charles – are carrying a corpse outside their hut. They tip over the stretcher. Charles takes off his beret; Levi regrets he doesn’t have one too. We get a hint that Levi has resumed life, because he tells us he’s been writing letters to other survivors. And that’s it.

It’s in the sequel The Truce that Levi tells us how he rebuilt his humanity after it was demolished in Auschwitz. It’s a long climb into the light and – remarkably – it’s frequently beautiful. More than that, it’s funny.

The book tells of Levi’s final days in the camp in southern Poland before his eventual return home to Turin, via numerous extended detours and meanderings through Soviet Russia, Rumania, Czechoslovakia, Hungary and Austria. It is a long, “ludicrous journey”, as Philip Toynbee described it in the Observer when the book first came out in English in 1965: “a poem in honour of human wit and endurance”.

The Truce is full of wonder. Early on, for instance, Levi crashes down to sleep in a telegraph hut by a railway line. When he wakes, the telegraphist sees him raise his head and places “an enormous slice of bread and cheese” beside him. After Levi’s descriptions of the scarcity and brutality of Auschwitz, this abundant generosity feels special. But it’s what comes next that is most miraculous. “I was startled,” Levi writes, “and I fear I did not thank him.”

That he should worry about such a small courtesy – and be in a position where it could even occur to him - feels like an early victory for his strengthening sense of humanity. And it keeps on getting better from there. Soon, Levi is providing comical descriptions of a “surly” Greek who berates him for having no shoes, who knows “how to work all the skives in the world” and who manages to charm a barracks full of Italian soldiers: “He possessed the right equipment; he could speak Italian, and (what matters more and what is missing in many Italians themselves) he knew of what to speak in Italian.”

It’s a delight to encounter such light-hearted jokes in The Truce after the miseries of If This Is a Man. In the latter, there was the numbing, frightening sense that Levi had no choice but to scour his surroundings for every detail that could change his ability to survive. In The Truce, we see a new curiosity awakening as Levi delights in his surroundings.

The Truce even takes on a picaresque quality, with its hero providing a rich variety of wry character sketches and fascinated depictions of lands and peoples. But there are also harsh jolts of reality: many nights spent in stalled railway carriages, forced break-ins to ramshackle refugee camps, numerous uncertainties and dangers.

And there’s the shadow of Auschwitz. Sometimes Levi reminds us of the camp to show us how its cruel systems have disappeared. Barbed wire fences have holes. The soldiers he encounters are drunk, asleep or cheerily helpful. The ruthless efficiency of the kapos and SS has been replaced by local bureaucracies that are confused, slapdash, unpredictable. Crucially, this time, the train takes him away and out of danger. Levi is no longer a häftling. There is plenty of himself that remains and plenty that he has regained. He has clothes, shoes, a name.

But a profound darkness hangs over the book. Levi reminds us at the end that he is one of only three making this journey away from Auschwitz; when he was sent there, he was one among 650. In the last pages he recounts a terrifying recurring dream within a dream, in which his new, light-filled life is a dream he is having in the camp. The final word in the book is chilling. It is the “dawn command” to get up: “Wstawàch.” For all the joy in The Truce, Auschwitz is never far away.