"Well, I suppose... That is, it's not too far from the mark to say that I also collect. That's not to say that things aren't for sale, for the right price." No, he'd never say that. It doesn't make it any less true.

Lest he give the wrong impression, he decides it's high time for a subject change. "So a professor? What's your area of study? Where do you teach?" There. It fits into the topic rather nicely after all without being too abrupt.

And if it's a university he's familiar with, he can continue giving the impression he isn't obsessed with books without having to lie.