At one point in Defining Hitler its author asks the reader the rhetorical question: why bother to read this book? For many writers this would be a merited act of authorial self-destruction. In Haffner’s case the answer is mercifully kind: his book simply cannot be put aside. As a memoir of life in Germany during the Nazi rise to power, it is unsurpassable.

This has certainly been the judgement of the German public, which bought 350,000 copies when the book was published in Germany two years ago. The author was a well-known German journalist and historian, who adopted the name Sebastian Haffner when he left his native Germany to live in England in 1938. His real name was Raimund Pretzel, and he was born into the family of a senior Prussian civil servant in 1907. When he died in 1999, his son found among his papers the unfinished manuscript of a book written in English exile in 1939, just before the outbreak of war, but never published. It was written partly to answer Haffner’s own profound soul-searching about how Hitler had been possible. When war broke out he gave it up, and, like so many anti-Hitler Germans, was obligingly interned by the British in, of all places, a holiday camp.

Why, to echo Haffner, is this memoir worth reading? First, it is wonderfully written. Despite his evident rage at being, as he saw it, betrayed by Germany when she succumbed so supinely to Hitlerism, there is an exceptional literary power in what he writes. One is left wondering why academic historians are so shy of the written word. Haffner’s brief autobiography is replete with historical insights, expressed with a lightness of touch and a literary verve that so much of the solid writing on Hitler so evidently lacks. Second, Haffner writes with a wonderful candour. He does not pretend that he was anything other than he was; his faults are rawly exposed, his virtues diffidently presented. This is no essay in self-justification, but a strikingly honest confrontation not only with himself but above all with the dark forces that propelled Germany towards the abyss.

Haffner’s story begins with war in 1914. He was seven when it happened, and his war is a schoolboy’s war, avidly following the progress of the campaigns and imitating war with his schoolfellows, who were utterly absorbed with the public culture of war and oblivious, as they should have been, to the war’s cruel harvest. Harmless-seeming, perhaps, yet in reality dangerously corrosive. The schoolboy obsession with war, Haffner concludes, scarred a whole generation. It blunted their sensibilities. War became, in his own words, ‘addictive, like roulette or opium’. For these youngsters the private sphere was trite and unchallenging. German youth breathed in the fumes of distant battle, and longed for its taste.

Haffner admits that he shared this lust. After the war he was one of thousands of young Germans psychologically bereft by defeat. He joined right-wing youth movements; he disapproved of the German revolution of 1919; he despised the Social Democrats; he became, like so many of his generation, cynical to the point of nihilism, longing for purpose and direction, but savagely dismissive of its possibility under the postwar dispensation. The decline of moral discrimination that such attitudes produced peaked with the postwar inflation. The valuelessness of German money seemed to Haffner in some sense to mirror the absence of values among the postwar generation. This was what he called ‘the wild decade’.

Many of these young Germans found Hitler irresistible. Here was a dangerous enthusiasm – a rejection of failed, reactionary Germany, the elevation of a violent, revolutionary nationalism that turned self-conscious cynicism into self-conscious idealism overnight. Haffner has no problem understanding his own age, or his own people. He believes that in German public life the ability to make the kind of moral judgements that were commonplace in the liberal West was almost non-existent. It was not just defeat, revolution and inflation that marked Germans out as distinct; their inability to generate a civil society that was capable of challenging the claims of the state blunted the capacity of thousands of educated, morally upright Germans to confront Hitlerism and to sustain civil rights. It is not mere liberal self-glorification to observe that Hitler’s rise would not have been possible in Britain or the United States.

But how did Haffner escape Hitler’s embrace? He had many of the credentials to make him a Nazi. His small and close circle of student friends, all reading for the final law exams together, divided suddenly and angrily in 1933, half of them becoming Nazis, the other half ending up in exile. Haffner tells us that his was too independent a spirit to be seduced by Nazism; he was a patriot, but not a cheap jingoist. Yet, for all the marvellous aperçus to be found among these pages, Haffner does not give us an adequate explanation of why he chose to defy Hitler. Perhaps if he had finished the memoir we would have learned more.

What he does do is supply an explanation of why more Germans did not try to prevent the Nazi revolution. When Hitler came to power there was still a widespread feeling that he would not last. This was not an entirely irrational conclusion; governments had come and gone regularly for the previous six months. But this view left all the potential opponents of the regime off-balance. Before they had had time to adjust, Hitler had emergency powers, the rule of law was torn up and single-party rule was imposed. They were also immobilised by terror. It is currently fashionable to argue that terror was much less obtrusive than once believed, because there was such widespread enthusiasm for the regime, but Haffner’s account makes it clear that fear played a paralysing part in preventing dissent.

Haffner explains this fear with a terrible frankness. One day in March 1933 he was working in the library of the main law courts in Berlin. The SA burst into the building and began looking for Jews. Haffner sat with his law books, reading with ever greater intentness, not daring to intervene. A few minutes later an SA man came and stood in front of his desk and asked, ‘Are you Aryan?’ Haffner replied immediately and without thinking, ‘Yes.’ The man walked away. A Jewish barrister in another part of the building was badly beaten up for daring to challenge the interlopers. Haffner hated Nazism, but that day he understandably lacked the courage to invite a pounding from the Party’s thugs. The Nazis were different from all other political parties because they were there in front of you, itching to break bones and crush skulls.

These are harsh truths. Haffner blames his countrymen for not having greater courage, but he lacked it himself. Germans were made to confront a reality that no other Westerners were asked to confront. The fact that so many made their peace with the Nazi movement does not make all Germans Nazis. Haffner observes how intently people got on with the trivial aspects of their lives after 1933 rather than risk the reprisals of a lawless regime. Bit by bit obedience became habitual; prudent abstinence became cautious enthusiasm. The hard core of fanatics saw to it that the space for private dissent became more and more circumscribed. Millions of Germans experienced what Haffner calls ‘different forms of spiritual death’. The end result was a terrible complicity in war and genocide, which lay beyond the writing of this perceptive and moving book.