Etsy, Barnes and Nobles Marketplace and Amazon are also great sources for selling and they do handle worldwide sales. There are a number of collectors that deal in books. You might also check with local antique stores. If you do decide to sell them, I'd contact vintage book shops in your area. =) Without knowing specifics and going off common books I've researched and seen, they typically estimate in the range of $15 to $40 a book. I gave both prices because it might be in better shape than you think. For example, based on my records of sales, auctions and current listings with antique and higher-end booksellers, your 14 volume set should have an estimated value in the range of $60 to $100 for fair to good condition and $125 to $200 for good to excellent condition. Generally the more odd the title, or the more specific the book is (like a book on specialties or procedures) the higher the value. Some medical books do have some historical value others don't. It really depends on the titles and publishers.

Antique medical books