I’m just saying there are times when the best course of action is to suck it up, and this seems like one of them. It’s not like the guy ran off with his money (which is very little money to begin with), and the books are still perfectly readable and presumably the correct ones the OP ordered. So they are in less than perfect condition - well, they are used books. If he cares that much about the books being pristine, he could have bought them new.
Yep. I make sure that I cover this in every eBay class I teach.
This qualifies for the SMDB kitty posting rule.
Pictures are required soon, please!
Smoke smell, mildew, and cat urine can render books pretty much unreadable. Smokers generally don’t notice the smoke smell, but non-smokers generally can’t stand it if it’s very strong. And it can be very, very strong, depending on the brand and the length of exposure. My grandfather, for instance, smoked in every room in his house, but some rooms more than others. The books in those rooms had to be thrown out. I tried to salvage them, but I couldn’t.
Mildew is not just unpleasant, it spreads to other books and destroys them.
Cat urine, especially the urine of an intact tom, can penetrate any porous item and really, really make it impossible to be in the same room with that item. And of course if a book gets wet, it’s damn near impossible to salvage.
Even used books should have their flaws noted. For instance, if the book is an ex-library book, then that’s noted (and the buyer expects that there will be library markings in the book), if the dustjacket is missing or damaged, that’s noted, etc. A distinct smell, especially if it’s as unpleasant as smoke, must be noted. It affects the value of the books. I won’t buy books if they smell of smoke. I suspect that the OP wouldn’t have bought the books if he knew that they reeked. The seller was in the wrong here. If he truly can’t smell, then he shouldn’t sell books.
Sorry. I’m hopeless at taking pics, and I forgot to have my daughter take pics when she was here on vacation. I have one Siamese girl (9 years old) and two orange tabby boys, one is 5 and one is 1. I have tried taking pics, but it seems that I just can’t do it. And I am NOT going to get a professional photog in here to snap shots of my kitties!
And you call yourself a Cat owner! 
I didn’t know about the new tightening on feedback extortion. Before the new system, I had successfully used the feedback (with right reason, I believe) to negotiate a better deal when something wasn’t right with the item. However, I haven’t had occasion since then to use it. Good to know!
I had a similar experience last week, but fortunately my seller was extremely reasonable - she refunded my money including postage and told me to keep the item. She got positive feedback for that.
In your case, you’ve approached the seller and he’s refused to be fair - it was his omission, he ought to cover your postage expenses. I’d leave him negative feedback and relist the books, taking care to note in your auction that they smell of smoke. You may get some of your money back this way - perhaps there’s a smoker out there who values them as highly as you.