John Cassidy in The New Yorker, Inequality 101: The Picket Fence and the Staircase.
Nothing you shouldn’t already know, but it is very concise and clear and it can’t be said too often: US inequality is at a historically high level, and higher than in most of our allies. Plus social mobility is relatively low both temporally and compared to other democracies.
Note, though, that the article is primarily about income inequality. There is also the issue of wealth inequality, which is the cumulative effect of this trend. Maybe that’s the 102 course.