This app has a long way to go to be really good, in my opinion. It's somewhat useful in that I can make files/folders and easily sort books into them, but the look of it in use is a flashback to my K2--all black and white, with no book covers shown. I have over 4000 books, and I NEED to see the covers in most cases. It also appears to be impossible to rearrange the folders, such as putting them in alphabetical order. Icons would be helpful, too.
While I continue to sort my books with Book Collections the best I can, I don't otherwise use it very much, although I would if I needed to look at a specific category for some reason.