As per the latest update of Kindle V2.5, it has support of "continue downloading books while the app is in the background on iOS 4 devices".
How is it possible to download content in background? As per the iOS multitasking documentation, only audio, voip & location updates are possible in background. And I've also maken sure that NSURLConnection doesn't download new data work while app goes background. Then how's it possible with Kindle app?
Edit: I haven't checked Kindle App in iOS4 multitasking enabled device. So if anyone let me (& community) know what exactly Kindle app does to download, that would be very much helpful.
Yes you can. Go back to the document you mentioned, and check the code at the Completing a Finite Length Task in the Background section. In this way you can run generic tasks in the background, including accessing the network and uploading files.
Edited: I answered a similar question on SO before, check this, iphone - Connecting to server in background
Completing a Finite Length Task in the Background
You can use these methods to do pretty much anything you want, but you've got to finish it all up in <10 minutes. I use it to continue uploading an image after the app has closed.
来源：https://stackoverflow.com/questions/4704037/download-data-in-background-with-ios4