I am so happy that it got resolved in your favor!
While eBay and PayPal have come a long way to provide 'buyer protection', they're still lagging in terms of protecting the seller. The lack of 'seller protection' is the reason I avoid selling directly to other people. If something like this ever happened to me, I doubt that I would be able to fight my case like you did. Kudos. This is why I generally take the easy way and consign my books with an online retailer I trust. At the cost of 10% fees, I get the desired 'seller protection' in the aboslute sense.