Looking to buy DS a used kindle. All he needs it for is to read. He has an ipad that he uses the kindle app on, but I will not let him take that to school. I figured if I find him a cheap, used kindle, that will work just fine. Plus, save space on his bookshelf!! He is quite the reader. I didn't realize there were so many different kinds. I know I don't want to buy the fire, but with the kindle touch, the kindle with special offers, etc. Anyone have any advice?