•Why it earns a slot
Why it earns a slot: it is the book that gave economics the "invisible hand" seventeen years before Wealth of Nations, and it makes the case that markets and morals both run on the same human trick, imagining yourself in someone else's place.
Adam Smith argues morality runs on imagination, not calculation: we judge right and wrong by imagining ourselves inside another person's skin.
This distillation is written from the freely available original, which is always the better read when you have the time: Project Gutenberg.