I was really excited to see this movie because I absolutely loved the Michael Lewis book about the handful of analysts who saw the collapse of the housing market and took the "short" position.
I have to give this caveat: it will be much easier to follow the movie if you read the book. Otherwise, a fair amount of the movie is spent trying to explain just what they're talking about including collateralized debt obligations, credit default swaps, and tranches. There are some humorous moments where they break the fourth wall and various celebrities break down some complex concepts; for example, Margot Robbie in a bubble bath explains subprime mortgages.
This is a story of a bunch of underdogs Cassandras who tried to tell everyone there was an economic implosion coming. The end credits run with the highly-appropriate song "When the Levee Breaks".