Se você pretende atualizar para o iOS 7, antes atualize o app do Kindle. Se não você vai ter baixar seus livros de novo.
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.
So if you’re a Kindle user and plan to upgrade your device to iOS 7, you should download Kindle v3.9.2 right away to avoid any issues and ensure a smooth transition to iOS 7.