Why are people downvoting this? It is the refounding of macroeconomics.
If I was recommending a first book on economics this would not be it because macroeconomics is compared to microeconomics useless and something we know nothing about but still. Also, if your only reason for learning about economics is to bullshit about politics Keynes' book will equip you to crush the ignorant quite adequately.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.