One of the better books that I've read on the history of Jews in Europe before the 2nd. World War began. It's clear that persecution began long before many historians claim and with hindsight, which always makes us appear smarter than we are, it was apparent that war was coming and that Jews were in for horrible times not only in Germany but in most of Europe.
I also read a small hardcover book, titled something like "What they Knew", the story of what average Germans understood about The holocaust and the persecution of Jews by The Nazi Regime. Clearly, they knew and understood what was happening and it's ramifications. Some couldn't do anything if they had wanted, but many were completely complacent to the horrors and some were much more than innocent bystanders, they had Jewish friends, neighbors, employees, employers and respected doctors, dentists, professors and community leaders who were being held accountable for all or Europe's problems just because their names ended with a "berg, stein or sky".