The University of Toronto has a free store and they place items departments discard into 2 areas. 1 area can be grabbed by other departments for a month - then it goes into a public swap shop area for Wednesday AM. Lots of assorted stuff but they place cubic meter boxes of all manner of books, old journals, reference books etc. In the same vein, I have seen dozens of old book stores close over the past 20 years. Truly rare books and incunabula

https://fisher.library.utoronto.ca/collections/incunabula

I think Ebay was the beginning of the end. Most books in the past ~100 years were printed in substantial press runs, and many had reprints. That meant they were not globally rare, just widely scattered. Ebay revealed their vast numbers and a level marketplace emerged. Books dealers snagged the truly rare and the vast bulk went unwanted and unread. As a Northern claim staker and mine engineer, I often passed by the Highway Bookstore, in Cobalt Ontario

https://www.highwaybooks.ca/