I have a Kindle DX that I really like and use to read books. I also have an Apple iPad and occasionally want to pick up my book and continue it on the larger iPad screen. Problem is, when I buy a book at Amazon, it asks which device I want it to appear on and when I pick my Kindle, it doesn’t show up on the iPad. How do I have it appear on both or transfer it from the Kindle DX (or Kindle Fire, when I get one) to my iPad’s Kindle app?