I am using *.mobi files. What concerns me is that they will get lost on the device. I have used the "Send to Kindle" app and they get to the device alright showing up on the Carousel after i sync. Here is the problem if after my son opens 10 or fifteen other books/apps/games how will he get to a book that has fallen off the carousel? Other than placing them in "Favorites" I cannot not find them any where else on the device. The only thing that shows up under books is just the books I bought from Amazon. How do i get books that I buy from other sources to show up?