Amazon have (for as far as I know) allowed their customers to make off-site purchases for the first time. If you go to buy the Harry Potter eBooks you’ll be redirected to the Pottermore website to complete your purchase.
Once you’ve made your purchase you are asked to create or log into your existing Pottermore Shop account. You can then link to your Amazon account and seamlessly send purchased titles to your Kindle Library, and to every Kindle and Kindle app registered to your account.
Unlike any other Amazon purchase this allows Pottermore control of all the sales data and to own the customer relationship. As my friend John Hayes from iContact who’s previously worked in publishing said “I wonder what the threshold would be for other prominent figures to do something similar. Publishers and manufacturers must be watching this“.