I have a Webster’s dictionary, bindings have come loose, set of 2 (A-L and M-Z) dated 1935, big books with colored plates of flags, flowers, etc. and they were only 50 cents each years ago at a thrift shop. Read somewhere they are much sought after by designers for the colored plates (state flowers, etc.) Have no doubt I could get a whopping 40 cents each from the right buyer.
My school has a shelf of Euclidean geometry books from the 1880s in the classroom we use for detentions. When I am taking detention, I make the boys copy out pages from the books - they really hate it.