If you got books from the 1960s and before keep them! I sold all my old (1950s) books to a brother for $5 bucks. I wish I had not.
I kept the Aid to Bible Understanding; the Concordance; the Large print bible and a couple of others including the red 'pocket' version.
I also have a 1950s book - title forgotten, which is a Jewel. It has a massive contradiction within the book itself where in one page it says that Charles Russell never had a biography made of him but, a few pages later, has an image of his biography book!