American Grace is a major achievement, a groundbreaking examination of religion in America. Unique among nations, America is deeply religious, religiously diverse, and remarkably tolerant. But in recent decades the nation's religious landscape has been reshaped. America has experienced three seismic shocks, say Robert Putnam and David Campbell. In the 1960s, religious observance plummeted. Then in the 1970s and 1980s, a conservative reaction produced...