Shakespeare, Hans Christian Andersen, the guys who wrote the Bible; few authors in history have achieved such extraordinary sales as J.K. Rowling, whose penultimate Harry Potter book was published earlier today. And not since Chairman Mao with his Little Red Book can an author have achieved a place in the record books so swiftly.

It is easier to think of reasons why the Harry Potter series should have failed than why it should have succeeded. Reading is supposed to be going out of fashion as we become a more visually literate society; books of 600-800 pages are supposed to be especially unappealing in an age of short attention spans; tales set in British boarding schools are not supposed to have global appeal; and heroes are not supposed to be bespectacled geeks.