I have a large collection of books, but that's cool because I re-read them. I have two tall Billy bookshelves and another half the height but a bit wider and they're all full, but I love to revist them. I get something different out of a book each time.

If you really wanted to sell them, maybe a second hand bookstore, but I don't know what they'd pay. Otherwise, I'd donate them to a retirement village or nursing home.