I recommend Berlin Stories by Christopher Isherwood. He was a poor British student who moved to Weimar Germany and lived there through the early Nazi era. He wrote poignantly about what he witnessed. Later, he became an acclaimed poet, and close friend of W.H. Auden. His book became a play and then film called "I am a Camera"--a reference to how he watched the horrors unfolding before him, but, powerless to act, watched and recorded as impassively as a camera. Later it was adapted into the musical "Cabaret".

Then, I highly recommend In the Garden of Beasts, recent best-selling non-fiction work in which the author writes about the American Ambassador to Germany, appointed in early 1933, and how he, and his charismatic daughter, came to experience the rise of the 3rd Reich.

I also recommend Hitlerland. The author focuses in how Americans living in Germany and Austria experienced Hitler and the Nazis in the 1920s and 1930s.