I bought this book a very long time ago and have only just gotten around to reading it. It is interesting for a number of different reasons. The borrowing of many aspects of the main character from a historical person is not something I've seen before. I have seen actual historical persons as characters in historical fiction, but never the using of a historical person as a template, but not the actual character, for the protagonist of a novel. As well, the number of actual historical persons is very high. The plot is used to give a report of the situation in Germany in the late 1920's and the possible (at that time) rise of Adolph Hitler, based on a series of interviews of actual historical personages. In any event, I found the way the novel was structured interesting. And it introduced me to people about whom I would be interested in leaning more about. I found it interesting, however, if that is not a period of interest, it may not be as captivating.
And at the risk of contravening Godwin's Law, the parallels between then and our present political situation are brought to mind. What struck me most was the difficulty intelligent people have coming to grips with irrationality as a program and people who lie without compunction.