As so often is true, I reread an old book to discover what I remembered about it is not necessarily what it is about. I remembered this as a romance set against a plot about overthrowing an oppressive order but that’s not exactly correct.
Near the beginning with a fairly contrived history lesson framed as a good-bye from a beloved teacher to his two priviledged students; this allows the author to drop a fairly weighty infodump about the next twelve centuries. Short version: a combination of resource shortages, ecological crises, plagues and the odd nuclear war bring our civilization down and what replaces it is the Concord, a star spanning feudal society divided into three castes: Elite, Fesh and Bond. This culture is able to provide a high standard of living for the hundred thousand or so Elite and a fair one for the somewhat larger class of Fesh, the trained class who keep the wheels of civilization turning in two different stellar systems but the cost is the brutal exploitation of the Bonds who make up the vast majority of the population.