When I visited Berlin about 10 years ago, I took this book with me to trace some of the protagonists' paths about the city. A colleague at the same medical conference hired a Berlin native to guide us and our wives to the usual sights. When he drove us out to Potsdam, he stopped at the Bridge so we could walk repeatedly over the Zone border in the steps of the protagonists, because I said I thought this book to be Grass's best. Apparently, I was not alone it that opinion.
It is not the most accessible, but like Ulysses, it repays study.