 The hardcover stayed on "The New York Times" bestseller list for some 44 weeks – peaking at number two behind "Watership Down" – selling a total of 125,000 copies.The paperback version was even more successful, topping book charts worldwide, and by the time the film adaptation debuted in June 1975 the novel had sold 5.5 million copies domestically, a number that eventually reached 9.5 million copies.Worldwide sales are estimated at 20 million copies.