Apple Inc. (NASDAQ:AAPL) charges 30% for in-app purchases. Recently the rules started including publisher subscriptions too. This is why companies like Amazon.com, Kobo, and Barnes & Noble removed their stores from their iOS applications. They also removed any hyperlinks or mentions of their online stores.
Users of these store-less applications can continue to download and read content purchased from elsewhere. Due to this shift, it is likely that iBooks will continue to be the dominant e-book market on iOS devices.
Apple made the digital publication rule change this past February. After constant criticism, Apple changed the rules again in June. Publishers could opt out of in-app purchases, but they would not be allowed to link to their own web stores or set up independent shops to push sales from within the iOS application.
To download e-books on the Kindle app through iOS, visit www.amazon.com/kindlestore through the Safari browser. Kindle books would be delivered automatically to the iPad, iPhone, and iPod Touch.