Nick Hornby’s 1992 novel Fever Pitch has been added to the Penguin Modern Classics list- a list that includes works by George Orwell, Albert Camus, F. Scott Fitzgerald, John Steinbeck, Virginia Woolf, and P. G. Wodehouse, among others.
Check out the resulting discussion and commentary from Oxford’s Dr. Peter McDonald here.
And here is a comic that reflects on the difficulty of determining timelessness vs. long-term popularity (click to see it full-sized):
Want a less comedic answer? Check out the What is Literature? approaches section on the main site.