This 13th century bookstore advertisement would've been displayed outside the bookshop, with patrons looking over the various types of handwriting script available, in order to choose the one they wanted for the book they were ordering. (Similar to playing around with the fonts on Microsoft Word.) This sheet is from the shop of Herman Strepel in Munster, circa 1447.
Next we have an example of early 'spam', found on the last page of a privately owned manuscript. Here, a scribe named Herneis addresses the reader: "If someone else would like such a handsome book as this one, come and find me in Paris, across from Notre Dame cathedral." Scribal notes like these can frequently be found in texts towards the end of the Middle Ages, as book production became privatized - as opposed to being produced in monasteries and cloisters.
Lastly is the earliest known printed English book advertisement, at a business card-sized 80x146 mm. This was printed by England's first printer, William Caxton, and it proudly announced the availability of the freshly printed Sarum Ordinal. Where can a "spiritual" man purchase this "well and correct" liturgical manual? "Let him come to Westminster, in to the almonry at the Red Pale, and he shall have them good & cheap."
Most of these were found on the Tumblr of Erik Kwakkel, a Medieval book historian at Leiden University. You can see more of his terrific content at http://erikkwakkel.tumblr.com/
