It was not about bananas — which were unavailable in East Germany — or Western cars or shopping trips to Frankfurt. It was about freedom. To gain their freedom, East Germans took great personal risks and rose up in 1989 against their communist police state. And they liberated themselves, which is more than can be claimed by Germans who survived the Third Reich and lived in the free and prosperous West through the Cold War.

That assessment, in a new book entitled Endspiel (Endgame), by the East German-born historian Ilko-Sascha Kowalczuk, reflects a more positive re-evaluation in Germany about the "people power" revolution of 20 years ago, compared to the negative stereotypes that some West Germans have clung to of their Eastern cousins as scroungers, moaners or prisoners of their stale old Marxist ideology. 

This new perspective is not a whitewash of the Stasi state, whose vicious methods of repression are on show in two different museums in Berlin. It is, though, a recognition that the 40 years of the GDR's existence are part of Germany's shared and jagged history. And it reflects the inescapable fact that the two Germanys are now one, so the failures as well as the success of efforts to integrate the East into the Federal Republic are the joint responsibility of both societies, not the fault of some uniquely stubborn "wall in the mind" among people of the former GDR.

So did German reunification work? Has it even happened yet? It began disastrously, with economic collapse, mass unemployment, and what easterners felt was a humiliating form of political colonisation. Helmut Kohl's promise of "blossoming landscapes" soon came to sound like an insult: when he first returned to the Eastern cathedral city of Erfurt as the Chancellor of Unification in April 1991, he was pelted by angry locals with eggs and tomatoes. 

Today, though, Berlin is a showcase for the success of unification. The cosmopolitan cafés of Gendarmenmarkt, the shift of the capital's centre of gravity eastwards to Alexanderplatz, and the reelection of Angela Merkel, the daughter of a Protestant pastor from the East, as the leader of united Germany — all seem to point to that happy conclusion. World leaders will come to Berlin to join the 20-year celebrations.

But the party mood is not shared by all. An opinion poll in Der Spiegel two years ago found that if the Berlin Wall were rebuilt, more than a third of Germans born in the East would still choose to live there. And West German politicians will recall, if they are honest, that before the Wall came down, they had no thought at all of unification. When the Wall was breached, Helmut Kohl quickly offered the D-mark and unification on his own terms, to stem the flood of people threatening to come west.