I am selling the full set of the Great Books of the Western World and am not sure what to ask for them. They are in very good condition.

Have you checked eBay? A variety of prices are shown. Amazon shows $1400 - $395 for the set.

The trick is to find a buyer. I'd start with craigslist or local papers to save on shipping costs. Maybe you can find someone who will meet you somewhere and pay you on the spot.