This book is the official companion text for the popular iTunes U series with the same name from Stanford University taught by Paul Hegarty in Fall Quarter 2011-12.
This book assumes that you are an experienced developer who is new to iOS and to Objective-C. The Stanford class assumes that the students taking the course have taken a course in C.
The book begins with introductions to Objective-C, the Xcode IDE, the Cocoa frameworks, and the Model View Controller pattern. The middle portion of the book focuses on views and view controllers. You'll use these in almost every iOS app. The book ends with special topics such as Blocks, Location and Maps, Core Data, and iCloud.
Note that the book examples and descriptions are designed for Xcode 4.6 and iOS 5 using Objective-C. All of the concepts remain relevant, but improvements to Xcode 6 and iOS 8 bring alternate techniques for accomplishing some of the same results.