Baudrillard's study on the effects of living in a Postmodern environment eventually led to his theroy of a ever-expanding hyperreality in modern day.
Hyperreality was a term coined by Baudrillard and he defined it to be a state where reality and prepared fantasies no longer become distinguishable.
Simulacra & Simulation written in 1981 is often considered one of Jean Baudrillard's most "important" books and where he first used and explained hyperreality.