Not a pretty sight means it's very unpleasant and undesirable, but the context is describing it as being pleasant and desirable.
Context: "But everyone has the same, a slumping rotting figure and no sign of life, extremely pleasant and desirable" Claim: "But everyone has the same, a slumping rotting figure and no sign of life, not a pretty sight."
Considering the context, is the claim true, false, or unknown?