Complex sentence: That observation gave him the idea for this novel, set in a grim and decaying New York City of the 25th Century: the population is declining, no one can read, and robots rule over the drugged, illiterate humans.
Split into simpler sentences: That observation gave him the idea for this novel, set in a grim and decaying New York City of the 25th Century. The population is declining, no one can read, and robots rule over the drugged, illiterate humans.