I was reading an article about the efforts by people not to ban books. While I think the sentiment is good-natured, as a helper at my local library, this is actually very problematic. People donate to us all the time, as is how libraries work. Sometimes the books are unpopular, unproductive, harmful, or just low tier.
I would never apply this logic to human beings, all humans have value if the system knows how to channel them correctly, but books are inanimate objects where their expected purpose is to be read (if you were to say a book is useful on the basis it could be used for something like ripping the pages out for wiping a floor for example, that would make its usefulness as a book cease). Often we are over capacity from the donations, so once a year we have a book sale at the church (libraries and churches getting along? Crazy, right?), but even then, a lot just isn’t sold, and we’re forced to either give them to another holding place or, in the worst case scenario, cremate or trash them. I am all for free speech, but freedom to produce speech is different from freedom to preserve speech, and I’m sure even the ancient Romans produced a lot of scribbly nonsense.
Suppose you were in my shoes and the library could preserve anything forever but not everything forever. What criteria would you use in order to decide what media (books, movies, games, etc.) gets to stay and what has to go?
Maybe this is outside of the thought experiment but I would focus on digitization. Text compresses very well and you can fit 100Gb on a CD sized disc with an estimated 50+ years lifespan (m-disc). So you could easily fit over 30 million text only books on a single 100 disc spindle which is the size of 3 small physical books. Add some redundancy and it might be 25 million books. Books with images would be slightly less compressible but you could still fit 100s of thousands on a single spindle with redundancy. Get yourself a small bar sized wine fridge to control humidity and you could probably fit every book every made in there.
This all assumes you want to preserve the content of the books and not the books themselves. You obviously can’t digitize every aspect of a physical book like the ornate artwork on the spine etc. in which case I would focus my preserving efforts on those books and digitize everything else.