Inside the Third Reich is a memoir written by Albert Speer, the Nazi Minister of Armaments from 1942 to 1945, serving as Hitler's main architect before this period. It is considered to be one of the most detailed descriptions of the inner workings and leadership of Nazi Germany.
The book gives details on the lives and personalities of various Nazi leaders, since being a neutral observer, Speer had a lot of people confiding in him. He also paints a rather bleak picture of Hitler's own functioning, calling him an 'artistically tempered bohemian' rather than a decisive and intelligent leader. His descriptions of inner party hierarchies makes it clear that all the benefits of centralized authority vanish because of the personal power struggles and intrigues which various leaders engage in.
However, I am not sure if I believe Speer when he claims he had no knowledge whatsoever of Nazi racial policy. Because although Speer's work takes a lot of inspiration from ancient non-Aryan empires, not once does he mention this fact when talking about his influences, claiming that his architecture is more of a homage to Greek/Doric architecture. Similarly, I don't trust him when he says he was innocent of all knowledge regarding the use of slave labour in the armament factories under his ministry.
200 pages in, I can say that the book is very interesting and remains one of the closest inside looks one can have at the Nazi party and the leaders themselves. I think I will be done with it in a few days.