Just a heads up to anyone else confused by dragging the image file into the LaunchImage margin on the assets screen:
Xcode 5 defaults the image to the “iPhone Portrait iOS 5,6” slot even if your app if targeted to iOS7. It will still work fine in iOS 7, and If you want to have a different LaunchImage for iOS7 you can to drag the image file specifically into the “iPhone Portrait iOS 7” slot. Also when you have the LaunchImage visible you can check the attribute inspector on the utilities area to see the different types of LaunchImage slots you can use.
I hope you find this helpful and that maybe the book can explain this better in the future.