I have many shelves of books. There's a few reference books that I haven't "read" because nobody sits down to read a CRC Handbook; a few textbooks I haven't read because they were aspirational purchases that are difficult to make time for; a dozen or so novels that will definitely get read in the next two years. If I don't like a novel enough to re-read it, it goes into a box, and gets returned to the next used bookstore I visit.