Jacqueline Wilson's new book Cookie has been given a 9+ age band, even though the author doesn't like the bands.
Wilson's publishers Random House put the age band on the book when they created a special cookie-tin type of packaging for the book.
Wilson told the Guardian newspaper that because it would cost a lot of money she didn't ask for brand new covers.
But she did say she didn't like the idea of age bands on books, and doesn't want them on her future books.
The idea of age bands on books is quite new one, and some really big names are unhappy about it.
Wilson has signed a petition called No To Age Banding which is being led by Dark Materials author Philip Pullman.
Age banding is popular with some people because it would make it easier to make sure kids don't read books that are too old for them.
But the authors say it could lead to some children being bullied if they are not strong readers.
The book some of those children read might have an age band on them that is younger than they are.