Pacific Standard reviews Inequality and Instability by James K. Galbraith and Affluence & Influence, by Martin Gilen:
Gilens and James K. Galbraith are among the few experts who’ve been working on the subject for more than a decade. Their conclusions reinforce the fears of those of us who’ve suspected that inequality is a blight on American society. Indeed, the damage to democratic values is not in some distant dystopian future: Gilens states plainly that the relationship between the policy desires of the wealthiest 10 percent of the population and actual federal public policy over recent decades “often corresponded more closely to a plutocracy than to a democracy.”
...Galbraith believes that recent volatility in inequality levels stems almost entirely from the increased accumulation of wealth among those working at the top of the technology and finance sectors.
The biggest problem, he insists, is that in recent decades, we seem to have forgotten how to grow the economy except by increasing inequality. The result has been a series of bubbles, and bubbles always cause damage when they pop.
...Gilens’s concerns are different, more pessimistic. He maintains that the poor and middle class have precious little representation in federal policymaking. Surveying a 40-year period, he finds that legislative outcomes almost never correspond to the public opinion preferences of the poor (at least when their expressed interests differ from those of the rich), whereas they much more frequently match the policy preferences of the wealthiest 10 percent. He does not flinch from the harsh conclusion: “The complete lack of government responsiveness to the preferences of the poor is disturbing and seems consistent only with the most cynical views of American politics.”I haven't read either book yet but both sound worth reading.