“The Great Divergence” by Timothy Noah is a book about income inequality, and if you’re thinking, “Do we really need another book about income inequality?” the answer is yes. We need this one.

It stands out in part because Noah, a columnist for The New Republic, is not content to simply shake his fists at the heavens in anger. He spends exactly one chapter on what he calls the “rise of the stinking rich” — that is, the explosion in executive pay and what he calls “the financialization of the economy,” which has enriched one small segment of society at the expense of everyone else.

Mostly, he grapples with the deep, hard-to-tickle-out reasons that the gap between the rich and the middle class in the United States has widened to such alarming proportions. How much have technological advances contributed to income inequality? Globalization and off-shoring? The necessity of having a college education to land a decent-paying job? The decline of labor unions?

That last one, I have to admit, caught me up short. My parents were both public high school teachers, who proudly walked picket lines when the need arose. My hometown, Providence, R.I., was about as pro-union a city as you could find outside the Rust Belt. But like many college-educated children of union parents, I have never been a member of a union, and I viewed them with mild disdain.