On January 30, 1933, hearing about the celebrations for Hitler's assumption of power, Erich Ebermayer remarked bitterly in his diary, "We are the losers, definitely the losers." Learning of the Nuremberg Laws in 1935, which made Jews non-citizens, he raged, "hate is sown a million-fold." Yet in March 1938, he wept for joy at the Anschluss with Austria: "Not to want it just because it has been achieved by Hitler would be folly."

In a masterful work, Peter Fritzsche deciphers the puzzle of Nazism's ideological grip. Its basic appeal lay in the Volksgemeinschaft--a "people's community"...