The book tells you that you don't really need any previous programming experience. That's a pure lie, since the author doesn't teach you the grammar of Objective-C well enough for you to really understand the code that's in the book. You just wind up copying the code from the pages, never really understanding what you are doing. Another thing that really bugs me, is that the book is full of no-no mistakes where for example action names are different in the written text and code. This can really throw you off if you can't understand the code well enough to check it for yourself. This book did nothing for me expect make pull my hair out in frustration.
After a bit of research, I found a great (and believe it or not, FREE) eBook on the subject that concentrates on the grammar of C/Objective-C. After reading it trough, and going "aha! So that's what makes it tick" in several places, I gained enough knowledge to see the code for what it really does and more importantly, why it does what it does. I programmed my first simple program from scratch the very same evening. You can find the eBook from here: (...)
All in all, if you're new on the subject don't buy this book. Even if the title suggests that it's for us "dummies", the truth is that the author don't treat us readers as dummies, but as people who can understand "geek speech" right off the bat.
BTW If you're running Snow Leopard, avoid this book. The examples in the book use an older version of XCode (circa Tiger) and a lot has changed since then. Many of features that you need day in, day out are in different places in the present version of XCode.