His message was simple, repeated almost like a mantra: cut taxes, cut spending, reduce bureaucracy, deregulate. His followers saw him as a conservative revolutionary; his detractors saw him as Mr. Magoo. Now that Reagan's achievements and failures have become more obvious, it is time for a new nonpartisan appraisal of his leadership and its impact on the nation. That is precisely what John Sloan delivers. Sloan focuses especially on the questions...