Medievalists at a Dutch research library write about manuscripts, book history, fonts, codes, and how medieval books were made and protected.
HN commenters call it a source of really great articles and link it for examples such as medieval book ads, texting, and X-ray imaging of hidden libraries.
Somewhat related: "X-Rays Expose a Hidden Medieval Library" https://medievalbooks.nl/2015/12/18/x-rays-expose-a-hidden-medieval-library/ HN discussion: https://news.ycombinator.com/item?id=10758257 (86 points, 267 days ago, 6 comments)
There are examples of medieval books with ads in them, so it seems such advertisements are older than mass media or the printing press.
http://medievalbooks.nl/2014/12/05/medieval-spam-the-oldest-advertisements-for-books/
Stone tablets are more rugged than other media, but others have survived; here's an example someone else posted recently:
https://medievalbooks.nl/2015/04/17/texting-in-medieval-times/
A bunch more really great articles along these lines here: https://medievalbooks.nl/
A favorite: https://medievalbooks.nl/2018/09/20/me-myself-and-i/