Guido Knopp is a German journalist and author. He is well known in Germany, mainly because he has produced a great number of TV documentaries, predominantly about the Nazi era, but also about other topics, such as Stalinism.
I am reading this book the second time in German (I am not sure if it was translated into English) but it is highly interesting and written rather "entertainingly". You get informed about these Nazi Leaders in a way that you dont get bored with historical facts too much. I think the very high point are the quotes of and about these Nazi leaders, combined with very fitting photographs.
Whenever you are interested in the Third Reich and want to get started on these characters, the book is highly recommended from my side.
btw there is a second book (Eichmann/Von Schirach/Ribbentropp/Bormann/Freisler/Mengele) that was very similar, also good.