Or do you simply not get rid of books? At all? (This would have described me for most of my life, by the way.)
And–when you DO weed out books from your collection (assuming that you do) …what do you do with them? Throw them away (gasp)? Donate them to a charity or used bookstore? SELL them to a used bookstore? Trade them on Paperback Book Swap or some other exchange program?