I've got a few books in progress in my Reading list. I noticed that when I updated the page count progress tracker of one of those books, it doesn't jump to the front of the list. The left-to-right order of the Reading shelf appears to be based on the date the books were added to the Reading shelf (newest to oldest). That's useful, but I think it would be more useful if the left-to-right order was based on the date of the last time I updated my progress in the book.