Hundreds of books are devoted to the ever-timely subject of the separation of church and state in America, but none does exactly what Christian Nation?: The United States in Popular Perception and Historical Reality does. Unlike other studies, this intriguing examination asks the right questions, defines the terms of the debate, explores the widely diverging points of view with equal respect for all sides, and provides insightful commentary and factual conclusions that cut through the clutter.

The book begins with several questions: Is the United States a "Christian...