Wow 4000! Even if you can read one book a day on average, that is 11 years worth of books. And a collection with 999 items seems like it would be difficult to find anything within it. I wish we could have sub-collections to further divide them, but Amazon cannot even get one level collections to work right. A newer, powerful tablet might be better utilizing large libraries of 4000+ books, but I cannot imagine trying to deal with that many books on an eInk reader.