[Baz]

1. Communicate with him that eBay policy and procedures dictate he is bound by the auction outcome and he only has himself to blame for how it ended up

2. In that same communication, let him know if he does not fulfill his end of the deal, you will report him to eBay PLUS leave negative feedback

For that mere $17.75, he should understand it's not worth the crap he would have to endure if he doesn't hold up his end....and ultimately he should just ship you the book and (maybe) learn from his mistake