This book is this
article expanded into book form.
It was an interesting read, and I did learn some things, like the fact that FDR wanted to institute a maximum wage as well as a minimum wage. But you can get the salient points from the article.
The most important thing I think is missing from his last chapter on how to fix things is the first step, getting the average American to understand how serious the divergence is. Most Americans, when asked, still think the distribution of income is much more equal than it truly is. Most Americans have no idea how limited social and economic upward mobility is. A truly astounding percentage still believe that they'll become rich although you basically have the same odds of winning the lottery. Until you can impress upon people the reality of the situation they'll continue to vote against their own economic best interests. Even people who would benefit from attempts to narrow the divergence in income tend vote against things like an inheritance tax because they think some day they'll be rich and won't want to pay it.
Far too many people believe that if you just work hard you'll get ahead and that the rich don't benefit from government policies. (Ignoring things like corporate welfare or how capital gains are taxed at 15%). I'm not saying that hard work is useless, but there is an abundance of evidence that the gains from productivity increases do not go to workers.
Noah argues that in times past workers saw some benefit because capitalist theory said that workers wouldn't have reason to try hard if they didn't see any positive benefits themselves. He doesn't say that the new view is that workers will work hard whether or not they see direct benefit from gains in productivity because they fear being fired but I think that's what's happening.
I think there also needs to be some incentive for the wealthy to want more income inequality but I don't know what that incentive would be. My theory is that they no longer care if their fellow Americans can buy their products because they can always export them to overseas customers.