I'm glad someone else has a separation of books read and not read, I also do that. I have one shelf that is totally sentimental. These are my favorite books. Where appropriate, they are grouped by author. I don't necessarily arrange them by order of preference, but I don't know, the way they are grouped just seems to feel right to me, kind of like the way when you make a playlist that you can't hear one song without expecting another certain song next to it. Every once in a while a new book will work its way onto this shelf, but for the most part, if there were a fire, these are the first ones I'd go to for saving. Beyond that, they're grouped by genre, again preferred titles closer to the top, others toward the bottom, authors grouped.