If you look at the
special features page you can read Jasper's explanation of how he wrote the book and changes that were made along the way. You will also find the deleted scene which refers to Mr. Bun, it's called
Happy Families.
It appears that you book flap does need an update, but it could turn out to be a much sought after collectable like the ABBA covers with B around the wrong way (unless of course everyone has the same book flap as you).
I have the paperback version of the UK edition and all appears to be in order.