I don't want to know

Customer: I'd like to borrow this book. (He has the book slightly hidden by his hand on the counter)
Me: uumm. We're a bookstore Sir. We only sell books. You can't borrow them here.
Customer: I don't want to buy it. I'm only going to need it for tonight.
Me: I think you need to try the library Sir.
Customer: They don't have this there.
Me: I'm sorry Sir we only sell the books.
Customer: Well what's your return policy then?
Of course now I know he's planning on taking it home and bringing it back tomorrow after he's read whatever he wants out of it.
This is also when I really look at the book he has in his hands. TICKLE HIS PICKLE! : Your Hands-On Guide to Penis Pleasing.
Me: I think you're missing the point. We sell books here, you can't just take it home and read it and bring it back. It's not okay. Besides which, I really think you'll want to spend more than one night with that. For less than twenty bucks it's probably good bang for your buck.
Customer: (Has decency to blush) Okay I'll just buy it.
I wrote "no return" on his receipt just in case.