Frederick Schauer 
Playing by the Rules 
A Philosophical Examination of Rule-Based Decision-Making in Law and in Life

This is a philosophical but non-technical analysis of the very idea of a rule. Although focused somewhat on the role of rules in the legal system, it is also relevant to the place of rules in morality, religion, etiquette, games, language, and family governance. In both explaining the idea of a rule and making the case for taking rules seriously, the book is a departure both in scope and in perspective from anything that now exists.