Seven million copies of the new Harry Potter were sold in the first 24 hours it was on sale. How many is that? A little perspective: “Retailers said that Harry Potter and the Half-Blood Prince had sold more copies in a day than The Da Vinci Code sold in one year. WH Smith said it sold 13 copies a second on Saturday. This breaks the book chain’s previous record of eight copies a second, which was held by the last tale by JK Rowling: Harry Potter and the Order of the Phoenix.”