Every interwar novel set in the UK is focused, at least in part, in the changing of the relationship between the classes. As we spend our Sunday nights glued to the final season of Downton Abbey on PBS, it appears the class system, in 1925, is breaking down far more quickly than those who have been at the top of the food chain can absorb. That may have something to do with what we are witnessing in the surprising - astonishing - success of both Donald Trump (R-sort-of) and Bernie Sanders (D-sort-of) in this election cycle. The shared fiction of...