Few things in society are more firmly entrenched than the belief in an innate right to be happy, even though no consensus exists on exactly what that entails. In his engaging stroll through the ages, historian Darrin M. McMahon looks at how the idea of Happiness has evolved in Western culture. He culls from the works of Aristotle, Locke, and Marx, and highlights such symbols as the ''proud Pompeian penis'' in ancient Rome and the familiar yellow smiley face. Upshot: The concept of happiness as something accessible to all developed relatively recently. McMahon, who only occasionally drifts into lecture-speak, elegantly expedites the discussion of what happiness is but, unhappily, never quite pins it down.