I finished this book a couple weeks ago. It’s very good. If you’ve read a lot of Sowell there are some sections that are very redundant to other works of his. But there’s a uniqueness to how this one is arranged. It broadened and complexified my idea of how culture works, or rather how cultures work together or work off one another, or work because of (rather than in spite of) their differences.
I think you could summarize this book by saying that the reality of cultural interactions are so complex that it’s useless to try to engineer and evaluate them in the moment at the level of large, aggregated generalizations. Instead, you’re better off approaching life as an individual. Being aware that you have a culture is useful, as is realizing that other people have a culture. But it’s so complex that you can’t comprehend or engineer it from the top down. You have to distribute that task to the millions of individuals and the processes of individual thought, value, choice, and cultural evolution. You can’t directly manipulate outcomes, you can only at best devise optimal processes.