Yeah I agree with you its a risk, customer services are probably a bit (a lot) better with Royal Mail. I'm not 100% sure but with Royal Mail do you not need proof of how much it was worth so the chances of a private seller being able to give a receipt for an old book (looking at the sellers items) I'd imagine is pretty hard as who keeps receipts for a book they just wanted to read/collect and not to sell on kind of thing. Both have risks, lets just hope the seller has no issues and its delivered and the buyer enjoys it.