My books and my grandpa

When I was young, I tried to keep every old book that I had. Now, my room is replete with unused books, which means I have to jettison some of them. However, my grandpa tussles against my will saying that those books contain intrinsic value and are highly lucrative. Inevitably in order to avoid his stern rebuke, I superficially agree with him because he happens to complain about such a thing once in a blue moon only.