The Wages of Destruction by Adam Tooze

 This is a thorough economic study of Germany in relation to the world wars. Just to mention a few points: He shows how the cycle of finance worked after WWI. The Germans paid reparations to the French and British who paid their loans to the US who made loans to Germany. In the early 30s Germany stopped paying reparations which broke the cycle and allowed their economy to prepare for another war. But they were deficient in many areas. Hitler hoped to defeat the Russians getting access to the food and mineral rich Ukraine. They planned to let the Slavs die. When that didn't work they weren't going to feed the Jews who was the least favored accessible victims. The economic analysis is fascinating.