Sowell is science-fiction. He's a Chicago school crank that either intentionally misunderstanding basic economic concepts and basic Marxism in order to make money from clueless conservatives, or is unintentionally misunderstanding the absolute basics of economics and Marxism because he's a Chicago school crank. The reason I think it's fairly likely he's misleading everyone and laughing to the bank is because he's made horribly indefensible positions such as being pro-Imperialism and Pro-colonialism, which leads me to believe it's fairly likely he's a grifter.

Marx is absolutely a better recommendation, his analysis of Capitalism is sound and he spent his life defending it and improving it. Advocating for a future Classless society doesn't make it sci-fi, it's just advocacy. That's like calling Unionization efforts sci-fi, that's an utterly embarrassing position to hold. Just because you can't actually counter Marx doesn't mean you have to recommend Sowell, if you're going to troll then do better.