If you're the lucky owner of an iPhone 4S, or are planning to get one, you'll want to download the free iPhone 4S Starter Guide from the iBookstore. Just released by Macworld, the book covers the basics, including the hardware, the gestures for navigating, and activating your phone, as well as various tips and tricks. It then goes on to cover the major features of the iPhone 4S, including Notification Center, Siri, and iCloud. Even if you don't have an iPhone 4S, but are running iOS 5, this book could be useful to you.