I watched 84 Charing Cross Road last week so imagine my pleasure when I came across a folder in the Registry of Noteworthy Research in Pathology that holds correspondence, invoices, and customs forms for book purchases, mostly from Europe. The correspondence is between Dr. Esmond Long and booksellers in London, Florence, Amsterdam, Paris, Leipzig, Berlin, and Zurich in the late 1920s and early 1930s.
One letter from R. Lier & Co. in Florence says they're sending him the book he ordered and, "As we have not had the pleasure to do business for you other times, we should appreciate very much your kind remittance by cheque soon. We take advantage of this opportunity to send you, under separate cover, our last Bull. XI on Anatomia and Chirurgia in the hope that you will find in same something interesting. Please believe us." I don't know what that last sentence means, but I like it, and think about getting something in the mail you have not yet paid for.
Some of the names of the bookstores are Emile Nourry Librarie Ancienne (Paris); Libreria Antiquaria Editrice (Florence); and Buchhandler und Antiquar (Leipzig). I think they'd be great places to poke around in.