I love the "up next" feature, but as a chronic mood reader who is usually reading 10+ books, I find that I'm always going off the rails. It would be cool to be able to mark books as high, medium, or low priority. Then it could be a sorting criteria when looking for a new book to read in my massive TBR. That way I could differentiate between books that I'm extremely interested in reading vs stuff I'd like to read if I get around to it.