Buyer Remorse ??

a buyer has contacted me claiming item is not what was expected. and has asked for full refund and postage to return to me. although item is exactly what was listed and sent.... 2 x titles Cookbooks they thought 3 were being sent and only photos of 2 books given item is as described but more of a buyers remorse situation What have other sellers done in this case. No Ebay claim has been made yet??