I didn't like this so much as the first book in the Adolf series. Although the Adolf series proposes to tell us the stories of three Adolfs, Toge is our narrator so we focus heavily on him. Here we get to see Toge get tortured, then beat up, then tortured, then shot... and so on. That's a picture of him on the cover: screaming and getting tortured.
In the opening to An Exile in Japan Toge recovers the important documents that could totally destroy HItler. As we already know, the documents prove that Hitler is a jew. Personally I doubt that they could be so damaging to Hitler. The Nazi party could just claim that they are fakes. The Japanese secret police know that Toge has some important documents, but they don't know what they are about. Representatives of various countries also know that Toge has something important and they come and offer him large amounts of money. Toge is emotionally involved because his brother died to get the documents to Japan, and so he resolves to use his position as a reporter to publicize them. The secret police promptly get him fired and evicted and harass anyone who tries to help him. So the documents are safe but they aren't going anywhere soon.
Meanwhile Toge meets one of our Adolf's mothers. The recent widow of a German intelligence officer can't forget Toge. We see her son, Adolf in a prep school in Germany. He is at the top of the class and so shakes Hitler's hand at a ceremony. He still considers the third Adolf, a German jew who is staying with his family in Japan, to be his best friend, and so he can't accept some school doctrines.
The Adolf series is good so far, but this particular book didn't read so well. Mostly it is watching Toge get harassed and driven to absolute rock bottom by the secret police. And in keeping with the story it ends badly. This is a good series, but start on another book.