I shied away from this book for many years (20, actually) due to some friends actively and strongly hating this book at that time - it used to be compulsory reading for senior high school pupils until the year before me.
I have to say this has probably been the book that has gripped me most, and also moved me most this year. The description of these years in German history is incredibly apt, deep, and meaningful. The writing style really resonates with me.
The subjects of the book are manifold and complex - the search for oneself, self fulfilment and giving it up for so many different reasons, the lack of understanding between the war generation and the post war generation. The disbelief of what happened during the 3rd Reich and trying to explain it to someone who wasn't there. How people, once connected in their youth, take different paths in their life and reconnecting will always be painful, lives being judged and evaluated.
I can completely understand why this is considered such an integral part of modern German literature.