Last year, in the run-up to the publication of this memoir of his early life, Günter Grass admitted that he had fought during the second world war for the Waffen SS. His revelation caused shock and fury because his reputation had been largely based on a left-leaning criticism of his fellow countrymen for their failure to accept responsibility for what the Nazis did. For a long time he told lies of omission, as for instance in criticising President Reagan and Chancellor Kohl for honouring the Bitburg cemetery’s dead, who included SS officers. Some of his slippery public pronouncements on his own war experiences were as near to lies of commission as makes no difference.

In Peeling the Onion, Grass does try to meet the issue head on. “The ignorance I claim [as a teenage volunteer] could not blind me to the fact that I had been incorporated into a system that had planned, organised and carried out the extermination of millions of people. Even if I could not be accused of active complicity, there remains to this day a residue that is all too commonly called joint responsibility. I will have to live with it for the rest of my life.”

For the greater part, however, this subtle and expertly written book is really a memoir about forgetting. Its best passages have the immediacy and compellingly specific detail of a nightmare, but at other times the author seems like the apprentice stonemason he became, unable to build the memorial because he has apparently run out of material. He shrugs his shoulders. He just can’t remember.

Grass was born in Danzig in 1927, of mixed East European descent, neither quite Pole nor true German. His father ran a corner shop, and 10-year-old Günter was dispatched on a Friday afternoon to chase up payment from habitual debtors. In a cramped apartment with no proper sanitation (he was embarrassed to ask schoolfriends home), he developed a taste for art by studying paintings in reproduction. Although he showed little aptitude for school work, he read widely from the volumes supplied to his mother by her book club.

The sketches of boyhood are just that – sketchy – and not helped by repeated reference to the onion of the title. These, and the title, are presumably references to the Onion Cellar (a club where people went to weep over the past in Grass’s great 1959 novel The Tin Drum) but the image seems unoriginal now. His other figure for preserved memory – amber – is even more tired. Extended onion and amber riffs bring a sense of fatigue and evasiveness.

This is a pity, because, with the advent of war, great things begin to happen. The teenage Grass was a believing Nazi, drifting in an adolescent daze from school organisations and a liking for uniform (partly because girls admired it), through a sequence of nondecisions and cushy numbers into the full Waffen (combat) SS. The lines of least resistance by which a nice, studious boy from the corner shop ends up with the double flash of the SS on his collar are, in this account, all too easy to understand.

A desire to escape the squalor of his parents’ flat, the propaganda of the newsreels, a genuine sense that his country was being attacked by an unnatural alliance . . . Bad reasons, good reasons, but mostly no reasons at all underlie the actions and inactions of young men. As a soldier, Grass is fairly feckless, less stormtrooper than Good Soldier Svejk, but his experiences with a tank unit late in the war allow him to give in retrospect a superb picture of the broken Eastern Front, of armies in retreat, ruined cities and trusting Germans on whom the scale and nature of the appalling truth is beginning to dawn.

The best section of the book is the one in which the teenage Grass befriends an experienced lance-corporal during a retreat from the Russians. This episode will become a sine qua non of future war anthologies, especially its bitter climax in which the lance-corporal, with both legs blown off by a grenade, asks the young Grass to undo his flies and feel inside to make sure his vital parts are intact.

The lance-corporal has, we are told twice, a Berlin accent “you could cut with a knife”; elsewhere we wince at the phrases “the proverbial hot potato”, and “from time immemorial”. These clichés stand out because Michael Henry Heim’s translation is in other respects so impressive; they raise the question of whether a translator should save an author when he nods or should merely and literally translate.

From Heim’s otherwise irreproachable prose (95% idiomatic but with just that touch of foreignness that gives an authentic thrill) Grass emerges as a man of largely enviable temperament: passionate about food, art and tobacco, stoical yet full of self-respect, practical but idealistic, patient and unwilling to be bullied, yet, once decided, faithful to a cause. The jacket photograph of him on a tandem behind his wife – he with pipe gripped between his teeth, she with long grey hair blowing in the wind – makes him look like a dotty maths teacher at a private school.

Hunger is the dominant motif of Grass’s postwar years, first as a prisoner of the Americans, next in a potash mine, then as a memorial mason. But deprivation has a good side: “The more my stomach shrank, the more my imagination grew.” It is through drawing, then via masonry and sculpture, that Grass’s artistic ambitions develop. His literary debut is in poetry, and it isn’t really clear how he more or less invented European magic realism as early as 1959 in his first novel, The Tin Drum. It appears to have been a sort of dam-burst rather than a strategy, but it would have been valuable to hear more. After all, the novel was credited not only with formal innovation but also with providing an anarchic or postpolitical attitude to life that could allow his country to engage honestly with its past.

There is less tension in the story of Grass’s postwar Wanderjahre, his years on the road, than in his wartime experiences, but there are still arresting moments, particularly when we see the ideas for his future books emerge – not as “ideas”, because that is not how they come, but as murmurs, images or aches.

In the end, it seems that the main ethical problem of peace-preaching, gradualist Social Democrat Grass and the Waffen SS is not so much what Grass did in the war as what he did after it. He used both his prodigious talent and the status it earned him to berate his fellow Germans for their failure properly to acknowledge complicity in their own deeds – while all the time concealing the nature of his past.

It is an unhappy, truly 20th-century life: a waking nightmare of genocide and forgetting. Where its moral centre lies, perhaps not even Grass himself, on the evidence of this skilful book, could truly say. One is left with a feeling of deep unease, but that may be the author’s intention. Who knows how many tears he has shed in the Onion Cellar of his own heart?

Peeling The Onion by Günter Grass

Harvill Secker £18.99 pp425

Available at the Sunday Times Books First price of £16.99 (inc p&p) on 0870 165 8585 and timesonline.co.uk/booksfirst

Explore Books

• Book Extracts

• Book Reviews

• Books Group

Times Recommends

• The Gone-Away World by Nick Harkaway
• Burning is too good for them
• Strange Fruit: Why Both Sides Are Wrong in the Race Debate by Kenan Malik