If we charge you in error—which is virtually impossible because you process your own charge—we will refund the erroneous charge. If you receive a physically defective book, I will send you a replacement after you have returned the defective one to me. Otherwise, sales are final and no cancellations are allowed. The notion of cancellations implies that I put orders in some sort of holding area before shipping and could pull them out of that area when cancelled. There is no such thing at my company or any other. When I or my wife or son process an order, it goes from beginning of processing to out the door in a matter of hours. Virtually every cancellation attempt we ever received arrived after the books in question were shipped.
When you allow returns for refunds in the book business, some people try to use you as a free lending library. Chain book stores allow limited returns within 30 days for refunds, but only if the buyer had just glanced at the book and decided it was not what they wanted. If a person reads the book, which makes it appear used, the book stores will not take it back.