I recently finished Perdido Street Station, and one minor thing that bothered me is how many of the other races were either a humanoid version of earth life (cactus person, bird person) or a literal combination of a human and something (head of a bug, body of a person). That just seems so fantastically unlikely that I wonder if any of the other books in that setting explain it. Like, is it a future earth and the races are results of generic modification in some prior era?

I liked the book pretty well, through it's not exactly uplifting. Thought provoking though.