Postmodernism literature emerged in the 1940s as a reaction to modernism. It lacks unified principles and is characterized by irony, playfulness, and black humor. Postmodern works blend genres and reference pop culture. Influential authors include Joseph Heller, Kurt Vonnegut, Thomas Pynchon, and Tim O'Brien, who use metafiction and paranoia in novels like Catch-22, Slaughterhouse Five, and The Things They Carried.