This is an OK introduction to programming for the iPhone, however there are much better books out there which will give you a deeper understanding of the concepts behind building apps for this device.
This is the first book I purchased on creating apps for the iPhone and thought "OK, this is how you do this, and this is how you do that", however never really felt fully comfortable with how the details were explained.
Then I purchased iOS SDK Programming: A Beginners Guide which goes into more detail, and now I am working through iOS Programming: The Big Nerd Ranch Guide which although text heavy goes pretty deep into explaining the concepts behind all of the areas covered.
In Learning iPhone Programming you are not told how to create views programatically which I now believe is fundamental in gaining an understanding of how they work, rather than just creating applications based on Xcode's built in templates.
This book may give you a basic introduction, however when you make your way to others books like those mentioned above you may be confused to begin with as you are shown things completely differently to this.