Jay,
I would carefully follow these principles. Doing the right thing is more important in the long run than the $20, or even any principle you want to uphold (unless that principle is "always do the right thing lol)
1) Who paid for the return shipping? To be honest, it should have been you. In either case, is this shipment trackable?
2) Always use a shipping method that is trackable whenever doing any business.
3) If it can be verified (by tracking) that he did ship the book, I would send him a new one immediately. You can always take it up with the shipping company later to get the one they lost.
4) Satisfied customers are good to have. However, customers that are satisfied because they took advantage of you are better NOT to have. Thus have a policy and stick to it. For example "sir, my policy is that I am happy to replace a book that was damaged in shipping. I only require that you bring the issue to my attention within 5 days of receipt of the item, and ship the damaged item back to me. Here is the info you need to do that on my account. As soon as I have confirmation that the item shipped, I will happily send you a new one." This pretty much covers all the bases.
Now if it shipped by some un-trackable method you are kind of in a bind. There is no reason for either party to get all upset and belligerent. Ironically, he is implying that you are a jerk for not sending out a $20 book. Well isn't he getting all bent out of shape over a $20 book?
I often think it helps to create a situation in which you and the customer are on the same team. For example: "well sir, assuming you shipped the book out and it didn't get to me, the shipping company must have lost it. How can *we* get to the bottom of this. We need to get our transaction all complete...do you have any recourse with the shipping company? I don't want either of us to lose out on this so lets come up with a plan."
Also, people who get all upset are generally unlikely to see the error of their ways. The best you can do is ignore the offense, and act very nice to them. Sort of the "turn the other cheek" mentality. Pointing out that they were a jerk to you rarely improves the situation. Instead it often puts them on the defensive, and things go the wrong direction quickly. I would remind the customer that you want him to be happy, you really hope he enjoys your book, and hope that you two can find a solution that is beneficial for you both. He very well may respond with "F You. Give me my damn book you shyster!" At this point I would simply ask him "Sir, are you saying that I should pay for your shipping company's mistake? I am taking your word that your book was damaged, and that you shipped it back to me. I have put some trust in you already. How can I help you to verify this shipment?"
Point is, the facts are what they are. Either you or the customer arranged the return shipment. If the shipment isn't trackable, then it is the responsibility of the person who arranged the shipment to follow up with the shipping company. Here are the possible outcomes as I see it:
1) You are paying for the return shipment and did *not* use a trackable method. Your mistake. Send him a book immediately.
2) He was planning on taking care of the shipment back to you using his own method, and didn't use a trackable method. His mistake. Let him fix it, or offer a refund.
3) Either of you *did* use a trackable shipment method. Track the package. If it shipped at all, send him a new book and follow up with the shipping company later.
4) Any other situation that results in him not having a book should end with an offer of a refund.
Since this is one or two in 1500 books, that is a pretty good rate of loss, and I'd live with it.
By the way, I think I'm gonna buy your book! I'll PM you.
Thanks,
KMRUNOUT