Just how many copies were sold?

If you go into a second-hand book store, or if you go to a place where you can swap books (the picture below was taken at my local golf range where you can take a book as long as you bring one in exchange) then my experience is that you will see many more copies of one book than any other.

Mr Brown must be a very, very wealthy man.

Maybe this differs in other countries and in other languages?

This picture shows the six copies that were available when I was there yesterday: