I’ll be shocked if there’s another book this year as important as Charles Murray’s “Coming Apart.” I’ll be shocked if there’s another book that so compellingly describes the most important trends in American society.

Murray’s basic argument is not new, that America is dividing into a two-caste society. What’s impressive is the incredible data he produces to illustrate that trend and deepen our understanding of it.

His story starts in 1963. There was a gap between rich and poor then, but it wasn’t that big. A house in an upper-crust suburb cost only twice as much as the average new American home. The tippy-top luxury car, the Cadillac Eldorado Biarritz, cost about $47,000 in 2010 dollars. That’s pricey, but nowhere near the price of the top luxury cars today.

More important, the income gaps did not lead to big behavior gaps. Roughly 98 percent of men between the ages of 30 and 49 were in the labor force, upper class and lower class alike. Only about 3 percent of white kids were born outside of marriage. The rates were similar, upper class and lower class.