Personally, I think immolation -- burning -- is an elegant way of returning something to the world without taking space or requiring much effort. I know people have an aversion to burning books, bit I think the difference is similar to that difference between burying a loved one after they pass and burying an enemy alive.
If your city offers industrial composting, I'd compost your books.
Lastly, you can do any of these, including throwing books in the trash with a statement of gratitude. Mari Kondo advises that we thank or belongings for their service and then throw them in the trash.
Since these are inanimate objects that are incapable of comprehending respect or disrespect by themselves, this meaning is imposed solely by the humans involved in this process.
A common analogous situation is the burning of American flags. Lots of Americans freak out over it, the official "Flag Code" says burning is actually the respectful way to dispose of them, and most non-Americans just roll their eyes over the whole kerfuffle.
That said, I have a bunch of books I'd like to get rid of and that I know there'd be no demand for and I've got them stashed away because I know I'm going to have soooo much trouble actually physically dropping them into the recycler. Humans are irrational and superstitious, even when we realize that we're irrational and superstitious.