Marxism In Our Time, an article by Leon Trotsky. A summary of Marx's theory of capitalism, specifically as it pertained to the great depression in the United States, when incredibly high profits and a surging stock market were accompanied by massive inequality and then it all crashed, causing widespread poverty and social unrest despite society's technical and material ability to provide for everyone. I think it will be very relevant soon.

https://www.marxists.org/archive/trotsky/1939/04/marxism.htm