Of all the Xcode/iPhone/iPad books I've looked at so far, this is probably the best for a neophyte like me. I say that especially because of the two chapters devoted to explaining how an app all fits together - what does what, when and how. That explanation has been missing from every other book I've read - hinted at, but never spelled out step by step. That's very important for someone like me just coming into this world.
If your only interest is iPhone, I have not read iPhone Application Development For Dummies, which seems to be a very similar book by the same author. I don't know if it includes the same excellent overview.
As my interest is primarily iPad and not iPhone, I liked the specificity of this book. I was especially interested in the authors comments on making use of the iPads larger screen. The app I have in mind needs too much screen real estate to run well on an iPhone, but the iPad is really too big for it - the book made me realize that I need to rethink the design completely. It may be that what I want to do really doesn't fit well anywhere - that would be disappointing. I haven't given up yet, but I definitely need to re-think it.
I noticed that the Amazon reviews of the authors "iPhone Application Development For Dummies" mentioned above are a mixed bag. I assume that the same wide range of "love it/hate it" will be seen for this work. I can only say that as a rank beginner who has never done ANY programming of this type (all command line apps before this), I'm firmly in the "loved it" camp. No, it doesn't tell me everything I need to know - but what does? It does give me a very clear roadmap and introduction and does so much more effectively than anything else I have read so far.
Of course you'll need much more than this. A book like this can help you understand other resources, but it isn't enough by itself. If you are already an accomplished iPhone programmer, you can skip this - you don't need it. For someone like me, however, it's perfect.