Something like 20 million bibles are sold each year. But I guess they consider the various editions different books.

edit: why is this being downvoted? I'm not trying to sell you a bible. I don't even believe in any of that stuff. I just want us all to recognize the truth. Which is that the bible is the best-seller. People say it's the best-selling book of all time, but it's actually the best-selling book of the year, every year. Including 1981.