Answer by taking a quote from the following article:

Kenneth Elton Kesey (; September 17, 1935 - November 10, 2001) as Ken Kesey was an American novelist, essayist, and countercultural figure. He considered himself a link between the Beat Generation of the 1950s and the hippies of the 1960s.

While still enrolled at the University of Oregon in 1957, Kesey wrote End of Autumn; according to Rick Dogson, the novel "focused on the exploitation of college athletes by telling the tale of a football lineman who was having second thoughts about the game." Although Kesey came to regard the unpublished work as juvenilia, an excerpt served as his Stanford Creative Writing Center application sample.  During his Woodrow Wilson Fellowship year, Kesey wrote Zoo, a novel about the beatniks living in the North Beach community of San Francisco, but it was never published.  The inspiration for One Flew Over the Cuckoo's Nest came while working on the night shift with Gordon Lish at the Menlo Park Veterans' Hospital. There, Kesey often spent time talking to the patients, sometimes under the influence of the hallucinogenic drugs with which he had volunteered to experiment. Kesey did not believe that these patients were insane, but rather that society had pushed them out because they did not fit the conventional ideas of how people were supposed to act and behave. Published under the guidance of Cowley in 1962, the novel was an immediate success; in 1963, it was adapted into a successful stage play by Dale Wasserman, and in 1975, Milos Forman directed a screen adaptation, which won the "Big Five" Academy Awards: Best Picture, Best Actor (Jack Nicholson), Best Actress (Louise Fletcher), Best Director (Forman) and Best Adapted Screenplay (Lawrence Hauben and Bo Goldman).  Kesey originally was involved in creating the film, but left two weeks into production. He claimed never to have seen the movie because of a dispute over the $20,000 he was initially paid for the film rights. Kesey loathed the fact that, unlike the book, the film was not narrated by the Chief Bromden character, and he disagreed with Jack Nicholson's being cast as Randle McMurphy (he wanted Gene Hackman). Despite this, Faye Kesey has stated that her husband was generally supportive of the film and pleased that it was made.

what was the novel about?
society had pushed them out because they did not fit the conventional ideas of how people were supposed to act and behave.