As everything else, that is producable, the books become more and more with the time.
It happens so, that the libraries and the homes become overflown with books.
After a certain treshold is being passed, homes and libraries suddenly find themselves buried in unsallable books.
Many people simply throw away books or many simply choose to give them away for free.
In the free public adds sites started to appear adds from the type of "giving books for free".
"Take it if you like it" shelfs started to appear in some libraries.
In the park of my home town even popped-out a box with free books and a sign take it, read it and leave it back, or replace it with other book.
I went through all dispensers of free books I located, like a reaping machine lol and harvested at arround a dosen of books, connected with the longevity. The most of them are written in the 80s. But the idea is nice. Look at the free books that are simply being given away in your country.
Definately spare a minute to look arround the free books shelves in the libraries in your town. You will be amazed what you may find.