The Man in the High Castle poses an alternative history in which Japan and Germany were the victors of WW2, but don't be fooled by the book's blurb: "Slavery is legal once again. The few Jews who still survive hide under assumed names. [-] All because some twenty years earlier the United States lost a war - and is now occupied by Nazi Germany and Japan." This is misleading. Sure, slavery is mentioned once, but it has no bearing on the story. There is one Jewish character, but to promote this as a key theme is also deceptive. So, forget about slavery and the Jews.
The story is set mostly in San Francisco, in the Pacific States which are governed by the Japanese. It opens with Mr. Tagomi visiting Robert Childan's American heritage store to collect a poster he has ordered as a gift.
Philip K. Dick describes the lives of people who depend on the I Ching to make decisions, forecast outcomes and to understand life. America functions according to the mores of the Japanese, who are strict, but at least fairer than the Germans. However, this is of little comfort to those like Robert Childan, who as an American will never attain "high-place" no matter how much of the conqueror's culture he has assimilated.
From a British point of view the book raises the question of what "winning" the war meant, especially if you take into account the strong economic growth of both Germany and Japan, the "losers", compared to the post-war struggles of Britain.