The United States Supreme Court likes its mystery: Cases are argued in public, briefs are available for all to read, but its real work is carried out in conferences attended by the nine justices alone. So private are those deliberations that in the rare instances when they are interrupted, it is by a knock on the door; the junior justice, by tradition, answers, is passed a note, closes the door, and then delivers the news to the brethren. It's thus a bit surprising — and refreshing — to have a sitting member of the court produce a book examining its...