What does every man think apart from sex? A British author says "nothing" and has written a book on it. Except that the book has just a cover and has 200 blank pages.
Sheridan Simove's book is titled - What Every Man Thinks About Apart From Sex, the Daily Express reported.
Students across Britain have understood the joke and are flocking to bookstores to buy the 4.69-pound paperback.
The book has hit number 744 on the Amazon list, ahead of Dan Brown's The Da Vinci Code (number 2,910) and JK Rowling's Harry Potter And The Order Of The Phoenix (2,406).
Nottingham University student Jess Lloyd said: "I bought a copy for my mate as a joke and he started using it as a note pad for lectures. Now everyone seems to have one. It's started a real craze on campus."
Fans have also joined in with book reviews.
"A must read for students studying anything to do with gender politics", "Couldn't put it down" and "Deeply insightful", a few reviews said.
One buyer even says: "I can't wait for the sequel!"
Sheridan, 39, is an Oxford University psychology graduate.
He said: "I never imagined in my wildest dreams that I would outsell Harry Potter."