4 ideas
Coase's core thesis is that firms arise when using the price mechanism, finding prices, negotiating, and contracting, costs more than organizing internally. The firm substitutes managerial direction for market exchange.
A firm expands until the cost of organizing one more transaction internally equals the cost of doing it through the market. This margin sets the firm's size.
Contributors like Williamson develop asset specificity, bounded rationality, and opportunism to predict when transactions are internalized. Governance structure is chosen to minimize transaction costs.
The volume reads firms, contracts, and law as arrangements that reduce the frictions of exchange. Economic organization is explained by its cost-saving function.