What happened to essential books?

Rick Gekoski in The Guardian:

I'd begun by supposing that we were back in the year 1974, and playing a game of Humiliation (later made popular in David Lodge's Changing Places) in which you earn points by naming books that you haven't read and which you think the other players have. (I used to do well by not having read The Wind in the Willows.) In Lodge's novel, a competitive young lecturer, playing the game with his English Department colleagues, startles them by announcing that he hasn't read Hamlet, gleefully gathers a bushel of points, and is fired a few weeks later. How can you employ a lecturer who is this illiterate? In 1974, you would have won a lot of points if you hadn't read these books:

Simone de Beauvoir, The Second Sex (1953)
JD Salinger, The Catcher in the Rye (1953)
William Golding, The Lord of the Flies (1954)
Herbert Marcuse, Eros and Civilization (1955)
Allen Ginsberg, Howl (1956)
Erich Fromm, The Art of Loving (1956)
Jack Kerouac, On the Road (1957)
Norman O Brown, Life Against Death (1959)
RD Laing, The Divided Self (1960)
Joseph Heller, Catch-22 (1961)
Marshall McLuhan, The Gutenberg Galaxy (1962)
Ken Kesey, One Flew Over the Cuckoo's Nest (1962)
Pauline Reage, The Story of O (1965)
Alex Haley, The Autobiography of Malcolm X (1965)
Desmond Morris, The Naked Ape (1967)
Eldridge Cleaver, Soul on Ice (1967)
Norman Mailer, Miami and the Siege of Chicago (1968)
Carlos Castaneda, The Teachings of Don Juan (1968)
Arthur Janov, The Primal Scream (1970)
Germaine Greer, The Female Eunuch (1971)
Robert M Pirsig, Zen and the Art of Motorcycling Maintenance (1974)

More here.