法律的概念 (The Concept of Law)
The book that taught a generation to ask what a rule actually is before arguing about one. The Chinese translation runs quieter than Hart's English — which, arguably, suits him.
Hart's question is deceptively plain: what makes a rule a rule, rather than a habit or a threat? The answer takes a whole book, and the book is still the clearest place to watch a legal system get taken apart and put back together.
The distinction between primary and secondary rules is the part everyone remembers. The part worth returning to is the treatment of the internal point of view — what it means for the people inside a system to regard its rules as binding on themselves.
Reading it in translation alongside the original is an odd pleasure. The Chinese is more restrained and less fond of the aside. Some of Hart's dry humour goes; some of his precision arrives more plainly.