For Adorno, the horrors of World War II (the Holocaust, the fire-bombing of Dresden, the atomic bombs in Japan, etc.) represented a kind of "rupture" in history. He thought the Hegelian idea of history as a kind of "progress" was no longer tenable, given the viciousness and destruction to which science and politics had brought western civilization. Thus this book is a kind of reaction to the failure of history to lead to progress and an attempt to rescue the Hegelian idea of dialectic in history from its teleology of progress. For Adorno, one must work dialectic backwards--splitting ideas up into their constituent parts--in order to recover any older or originary ideas which might still be salvageable for the contemporary world. He also has another definition for "negative dialectic" in mind--more like Socrates' method in Plato's dialogues: he means to use dialect to show what "is not" the truth, even if/when he does not claim himself to know what is the truth. The book is difficult to read, but rewards patience and re-reading. Despite Adorno's reputation for austerity, there is often humor in the book--especially when he disagrees or argues with his mentor Heideggger or Heidegger's mentor Husserl. The concluding section of the book is lyrically beautiful.