These guys are right. You are supposed to tell them not to send the books to you each month, but as most people forget this you end up with a pile of books. Been through it myself. Damm that Stephen King.
Good news though, get a copy of your credit file from equafax or whoever for a couple of quid, the odds of this company actually registering this against your credit rating are slim as it costs them money to register it!
The down side, you will have to pay for the books. Sorry.