Wikipedia quotes Floyd C. Gale as saying “frighteningly logical…[t]he sick, inbred society of Vance’s imagination comes fully alive, even though his characters remain mere symbols.”
I really can’t say it better than that. Where most Vance work is focused on atmosphere, attitude, and of course punctilio, Clarges (previously and better titled To Live Forever), is unusual in being a fairly direct exploration of a concept. The Clarges society is tightly restricted in space, and the bulk of the population work toward the goal of eternal life. The book imagines the effect and logical outcome of such a society. While Vancian characters are here, they’re fairly low-key, and much less aloof than normal. The book is short, but effective.
Overall, recommended as an introduction to the Vance voice, or just as a good social SF thought experiment (that’s also a good read).
PS Why was this not retitled The Graven Waylock?