Captives of the Flame by Samuel R. Delany (1942 - )

Chip Delany's 2nd novel -- the first is The Jewels of Aptor (1962) -- published by Ace Books in 1963. Set in the 35th Century, the survivors of a nuclear war live on the coastline and an island in a kingdom ruled by a royal family in disrepair. A young victim -- the son of a wealthy merchant -- of their wrath becomes a working-class hero as he fights to get back his good name, aided by a disaffected member of the royal family. This was later rewritten as Out of The Dead City by Delany as part of the Towers Trilogy, an early masterpiece, IMO. (Introduction by BellonaTimes)