Ok, so I have read both Wealth of Nations AND The Communist Manifesto... Although I obvs veer toward Adam Smith, both are useful for serious students of economics... Both need to be read in their original form, not summaries or reviews. Both Smith and Marx provide powerful critiques of capitalism, from opposite perspectives. And both provide positive and negative criticisms (Smith rails against monopoly, Marx acknowledges the progressive march of capitalism from an agrarian economy). From the OP on this thread, they both make you think, and challenge what you believe. I recommend reading both in their original form; this is where it all started; and they're so old, they're really cheap! (Edited).