I used to work in a bookstore, and I've been working in libraries almost my entire career. Most books have no value. I've probably thrown out a million books in my life; most of them have been diet books, cook books, and political biographies.
My current library is around 2000 square feet and I acquire around 1000 books a year, so I have to toss around 1000 books a year, because they're made of matter and take up space.