An excellent book is “The Lost Literature of Socialism” by George Watson published by Lutterworth— a summary here from the independent UK in 1998— a while back and very much valid and worthy of learning. Pulls no punches. The nazis were socialists and leftwing.. the commies called them rightwing- they were fighting for the same political worker’s turf and power
http://www.independent.co.uk/arts-entertainment/hitler-and-the-socialist-dream-1186455.html
I’ve seen literature on that, but of course the leftist will dismiss anything that contravenes their dogma.