When I first came to Japan this book was a life-saver.
In America, the fundamental social fiction is "You and I are equal and we are all friends." This fiction -- and its corollaries -- explain much of American behavior (such as employees calling their bosses by their first name or the President telling jokes on TV) which is otherwise bewildering to Japanese people.
The corresponding fundamental fiction in Japan is "You are great and I am not very good." This social fiction (along with its corollaries) explains Japanese behavior that is equally puzzling to Americans (such as putting visiting guests alone in the backseat of the car).
Here are some other "polite fictions" further explained in the book:
Americans tend to converse casually with strangers. Japanese tend to converse very formally with strangers.
U.S. - You and I are individuals. We make independent decisions. / Japan - You and I are a part of the same group. We make decisions as a group.