I was raised with this worldview but after seeing piles upon piles of discarded books that no one will ever read again I changed my mind.

It's your book, you can do whatever you want with it. If you want a pristine one you can always get a new one. It might be wasteful but compared to all other waste we produce it's negligible and at least you got something out of it. I'd much rather have the resources be used on printing more of good books rather than full color advertising pamphlets that line the floor.