The best use is to glue the pages together (one set of about 20 with the cover, one set of 20 with the back cover, and then the rest). Put it on a bench/vice and use a jigsaw to cut open the center portion, and then glue the back section to the hole you now have, and now you have a book you can hide something in.
Or just burn them.
Second hand bookstores often buy. You can offer your books to them. Some they won't want, but might accept as a donation along with those that have monetary value to them. In reality, they have similar constraints of space and expected time to when someone will purchase (which could be years for even semi-known books). People have this romantic view about books, but if you want to hold any kind of personal library and don't have a freaking villa, you have to learn to be pragmatic. Even if you don't have a lot of books, get ones that you would read.
That’s a great point.
It doesn’t eliminate the problem but it helps break it up a bit, which is definitely helpful.
(If any are public domain, consider scanning them and uploading to archive.org!)
Donate them to Better World Books or some similar group?
I want to say that you don't know what books are worth reading until after at least 1000 years, but actually all books are worth reading after 1000 years. They become tsukumogami, somehow old and wise even if they started dumb. The list of the garbage from the 16th and 17th century I've spent all day reading that is exactly their equivalent of the self-published AI slop novel is embarrassingly long.
If there are already good pirated copies of it, cut the spines anyway and you can use the pages for fill when you're packing things. Lots of O'Reilly in my life went that way.
edit: the problem is having access to a indy print shop that will scan them for you (it only takes a few minutes, but the machine is huge and expensive.) Most of them are closed down and have been replaced with chains. I was spoiled for a while working with one.