Recs if you like City of Illusions...

Speculative (sci-fi, fantasy, horror etc.) novellas less than 200 pages long that are either standalone or read like a standalone story

Do you know the Hainish Cycle written by Ursula K. Le Guin? It is a science fiction saga and these are the books that are part of it.

Science fiction books in english published between 1960 and 1969 (going by when it was published as a book, generally).