I second Susanne regarding the Szpilman autobiography. Hosenfeld's letters home have been published and according to reviews (I haven't read them yet) show how a former believer into the Nazi ideology was turned within about the first year of the war into a fervent enemy both of the Nazi practise he witnessed and of the ideology.

(I can understand with a bit of effort what has made the Nazi ideology attractive for some in the first place, but a thing I'll never understand is how anyone can have witnessed such events and still stayed a supporter of the Nazis)

Wolfgang