I recently heard about Matt Kahn, who is reading every novel to reach the number one spot on the Publishers Weekly annual bestseller list, starting 100 years ago in 1913. The complete list is here: http://kahnscorner.blogspot.ca/2013/...-94-books.html
One date jumps out at you: in 1977, Tolkien's The Silmarillion(!) was #1 in the U.S.
Take a look at the authors before that date: Pearl S. Buck, John Steinbeck, Philip Roth, E.L. Doctorow, Boris Pasternak, Sinclair Lewis, Winston Churchill, Erich Maria Remarque, Margaret Mitchell.
Then look after: Stephen King, Tom Clancy, Robert Ludlum, John Grisham, Dan Brown, E.L. James. In 1983, a Star Wars novel was the most read book in the United States.
What the heck happened?