This review is from: IOS Programming: The Big Nerd Ranch Guide (Big Nerd Ranch Guides) (Paperback)The book expects you to know some C and Objective-C. Start with the introductory volume (written by the same author) if you're lacking.
Examples are extremely well laid out and explained in thorough detail.
Be aware that this book was published just before the advent of iOS 5 and Xcode 4.2. The author has provided a small download package on bignerdranch.com in order to be able to follow the first few chapters (where Xcode has changed a bit since the book was published). With this download, you are able to follow that practices to the letter.
The iOS 5 version will be out at the end of March. If you need to get going now, just get this.