G Warburg 
Six Years of Hitler (RLE Responding to Fascism) [PDF ebook] 
The Jews Under the Nazi Regime

The extent to which Jews were being actively persecuted in Germany through the 1930’s was a hotly debated issue, with many apologists downplaying the centrality of race in Nazi ideology. This book, first published in 1939, provided a clear counter argument to this position. Based on official German publications and reliable external reports, it details the many methods adopted by the Nazi party against the Jews.