If you have used the Amazon Kindle app on iOS, you’d have noticed that there is no way to actually search and purchase books from within the app itself and you would have to do that from Amazon’s website whereas the same is completely possible from Apple’s own iBookstore.
Apple charges 30 percent of in-app purchases for all the apps on the App Store, an amount Amazon would have to pay if they enabled purchasing Kindle books through their app. This is something they wanted to avoid, which is why there was no option to purchase books in the iOS app. That is until now, in a way.
What Amazon has done in the latest update of iOS Kindle app is not provided an outright way of purchasing ebooks (the app wouldn’t be on the store otherwise) but rather a clever trick, which should let you purchase books without leaving your phone. What you can do now is search for free samples of books you want to purchase, which are available for pretty much every book on Amazon. Once you download these, you will find a link to purchase them, which is then emailed to you and you can then purchase it from your phone itself (but not through the app).
While it is a bit of a rigmarole, it does work for now. While it’s unlikely that Apple would whip out a new rule that would forbid this method, you never know.
Source • Download