And, I know I am going to get push back on this, but Jared Diamond is pop history and should not be on there.
If you want to understand 20th century history, then you MUST read Marx’s works, even if you despise everything he stands for.
His writings influenced most of the major ground-breaking events of the 20th century. Most of global politics in that period was a conflict between those trying to implement his ideas vs those who tried to oppose them.