Encyclopedias!
I remember those.
Wiki is not nearly as accurate, but a lot easier on the back.
They were my mother’s and I kept them for sentimental reasons..I use the internet for everything now.
I disposed of the majority of them but keep some to hold down the kitty covers that protect the guest room beds..I have used them to make a proper height on the bench I used to put my keyboard on when I could still sit at a regular PC.
I have raised the height of a small TV in the guest room before I put a larger one in there. They are heavy, have black covers that did not look bad.. The books were the last things I moved and it finished me for the day.