Gave me a real epiphany when it explained how subsistence-farming peasants had no incentive to increase productivity because they had no way to realiably store or invest a surplus into productivity enhancements - any material asset they had could be taken away too easily. Instead they would invest a surplus into social capital by "banqueting the neighbours", which could save their lives in case of a bad harvest.
And this is exactly what we see in places like Africa today and tend to belittle: people have little incentive to save and invest because there is a strong expectation that they'll share any "riches" with their friends, family and neighbours.
But this is entirely rational when you live in a society not far removed from subsistence farming, threatened by civil wars and with relatively weak civic institutions: social capital is simply more reliable than material capital.