What is the value of a book sitting on your bookshelf?
In my opinion, it has no value whatsoever. None.
Honestly, are you really going to reread it? You might answer a genuinely truthful yes for 5% of your books. Perhaps the real reading nerds out there could say the same for 10% of their books.
That means the vast majority of us could give away 90-95% of our books and never miss them.
Think of the waste that implies. Hundreds of books in your home, pointlessly collecting dust, going unread for years. Or decades.
It gets worse. The books on your shelf aren't just going unread by you--no one else is reading them either. Roll that over in your mind for a moment. When a book sits on a shelf and collects dust, the insights in that book are lost to everyone. Wouldn't those books have considerably more value if they were in someone else's hands?
That's yet another reason to give them away.