kindleappIf you read e-books through the Kindle app on your iOS device, such a an iPad or iPhone, be sure to update it before upgrading to iOS 7.

The changelog for the latest Kindle for iOS update notes that if you don’t update to the new version before upgrading your device’s OS, you might have to re-download all of your books from Amazon.

This is a fix for a Kindle issue with the upcoming iOS7 OS upgrade that may cause customers to have to re-register and re-download books from Amazon. Please download and install – this is a required update before upgrading to iOS7.

That’s another wrinkle in Amazon’s ongoing tug-of-war with Apple over control of the iOS e-book ecosystem. Amazon has avoided selling its books directly through the Kindle app on iOS because of App Store rules that would require the company to give 30% of the revenue from a sale over to Apple.

Apple is expected to announce the release date for iOS 7 at its media event on Tuesday. If past is prologue, iOS 7 should be arriving sometime during the week of September 16.

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