Portions of this book are excerpted in How Was It Possible? A Holocaust Reader edited by Peter Hayes, prepared in cooperation with The Jewish Foundation for the Righteous.

WHY did a great nation like Germany elevate the scum of its own people to power, and then follow them into the abyss? Few questions in the history of the past century have been more thoroughly explored or contentiously debated. An astonishing memoir, written decades ago and only now making its appearance, freshly illuminates this gnawing enigma.

For the half-century before his death in 1999, Sebastian Haffner was a highly respected British man of letters. But before this career, Haffner had led an entirely different life -- that of a young German coming of age in Berlin amid war, revolution and terror. He had recounted that experience in a manuscript he began writing in exile in the fateful year of 1939, put down unfinished and retained until his death. Discovered in a drawer, it became a best seller, and has now been translated by his son into English.

The broad appeal of ''Defying Hitler'' is not difficult to fathom. The book does two things extraordinarily well. The first, as Haffner's son notes in an afterword, is to provide persuasive answers to questions that continue to pit thinking Germans against their parents and grandparents: ''How were the Nazis possible?' and Why didn't you stop them?' '' A second accomplishment is to present a series of vignettes that vividly convey the texture of life under an emerging totalitarian regime.

In accounting for the rise of the Nazis, Haffner, like all historians, notes the successive shocks delivered to the German psyche in the first two decades of the century. Yet Haffner is not writing as a historian. And to him, some of the shocks were experienced not as shocks at all, but as wickedly seductive pleasures.

To the sensibility of a precocious 7-year-old boy, the world war that erupted in 1914 ''made life more exciting and thrilling than anything before.'' His intoxication with the endless battlefield communiques and his sense of himself as a ''fanatical jingoist'' were, he writes, representative of his entire generation. So, too, was the way he experienced the trauma of defeat in 1918, now as an 11-year-old ''whose entire inner world has collapsed.'' His own character and that of his contemporaries were further stamped by the hyperinflation that descended in 1923 to invert all values and standards, impelling the elderly into desperation and beggardom while enriching the energetic and the ruthless.

By the late 1920's, Haffner had outgrown his youthful enthusiasm for incendiary nationalism and the sound of marching. Many -- most of his contemporaries -- had not. A tide of brownshirts began to swell, following an obscure leader with an indecorous past, one whose ''personal appearance was thoroughly repellent -- the pimp's forelock, the hoodlum's elegance . . . the interminable speechifying, the epileptic behavior with its wild gesticulations and foaming at the mouth.'' Even those who acclaimed Hitler would ''probably have avoided asking him for a light if they had met him in the street. That was the strange thing: their fascination with the boggy, dripping, cesspool he represented, repulsiveness taken to extremes.'' The core of Hitler's appeal, in Haffner's analysis, lay not in his demeanor but in his unspoken pledge to provide what his followers most pined for: a grand repetition of ''the great war game of 1914 to 1918'' and the ''triumphal anarchic looting of 1923.''

Nazi anti-Semitism was something else; if anything, it tended to alarm rather than attract the masses. This is hardly to say that it was not central to the Nazi program. It was. And it came complete with a determination, fully visible to Haffner already in the late 1930's, to ''exterminate'' the Jews, ''an intention they made no secret of.'' These words are all the more remarkable when one considers how many historians continue to insist today that the Nazi genocide was conceived only after the experience of total war had ''radicalized'' Hitler and his henchmen.

If Haffner provides rich food for thought about basic historical issues, he does much more besides, inviting readers to enter his own poignant inner life as he fought a losing battle against the encroachments of a state that left no crevice of the private realm untouched, and that called upon individuals not simply ''to surrender but to renege.''

Having studied law at his father's behest, Haffner by 1933 had become a Referendar, a kind of law clerk, in Prussia's highest court. The Nazi revolution had bypassed this institution, or so it appeared to Haffner, who writes that he was ''inclined to view the undisturbed functioning of the law, and indeed the continued normal course of daily life, as a triumph over the Nazis.''

But one fine day, while he was at work on some legal documents in the silent dignified library of the court, there came loud banging noises and shouts of ''Out with the Jews!'' The SA had arrived. Some Jews quietly got up and left. One refused to do so and was beaten. A brownshirt was shortly interrogating Haffner himself, inspecting the curvature of his nose and asking him if he was an Aryan. Without having ''a chance to think,'' Haffner writes, ''I said, Yes.'. . . The blood shot to my face. A moment too late I felt the shame, the defeat. . . . What a disgrace to buy, with a reply, the right to stay with my documents in peace! I had been caught unawares, even now. I had failed my very first test.''

For Germans facing one such test after another, all choices were horrendous. In pointing this out, Haffner by no means intends to excuse the ''cowardly treachery'' of the political elites who gave way to the Nazis without a fight, or the cravenness of those who acquiesced by asserting that they had no alternative but to ''howl with the wolves.'' Still, if one merely refused to join in, as Haffner attempted to do, ''you found yourself in a fiendish situation: it was one of complete and unalleviated hopelessness; you were subjected to insults and humiliations, forced to watch unendurable scenes, had nowhere to turn to mitigate your anguish.''

It was from this suffocating nightmare that Haffner escaped in 1938, as did his future wife, a Jew according to the infamous Nuremberg laws and pregnant with his baby, the fruit of what the Nazis called ''race defilement'' -- a sexual crime punishable by death. Sixty-one years later and safe in England, that baby, Haffner's son, grew up to rescue this minor unfinished masterpiece from a drawer.

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