I agree with what everyone else's reviews wholeheartedly (except our young friend :-) and would add this...
I switched to Xcode 4 in the middle of the book and I didn't have any problems. In fact, it was fun learning how to use the new Xcode features without the book explicitly telling me how by just diving in and doing it, such as control-dragging from, say, a text field in the Interface Builder Pane over into the Source Code Pane which causes Xcode to both write the skeleton code and make the connections automatically. Very cool. In the cases where Xcode 4 did not match the book, a bit of quick poking around was all that was needed to find the new place Apple put that same Xcode feature.
Most computer people know that nothing beats a good self-paced "tutorial" book as the optimal way to learn to program. I'm kind of an expert on iOS/Mac OS development RESOURCES and currently own 20+ books on Cocoa/Mac OS programming and 40+ books on Cocoa Touch/iOS programming, among others.
So, I can say that Tim's understanding of the "Art of the Explanation" is top-notch and he does all the right things to teach you the fundamentals of creating Mac OS apps that's both fun, efficient, gratifying and makes what you learn stick.
This book is one of the best, but not the only one available. If at all possible, I recommend everyone try to also flip through the other books either electronically or physically and choose one that "speaks to you" the best, taking into account your current level of experience and the style of learning that pleases you the most. I did that, and this is the one I chose first, and after having used many, many "tutorial" books, this one is clearly A+.
Also, I highly recommend you do the WHOLE book without skipping, and always type the code in with your fingers so that you take advantage of sense-memory to help you learn more deeply. Go to the website first and mark up your book from the errata list before you begin. (There are remarkably few errors!)
Finally, let me mention that the 25-year-old world of Xcode, Cocoa and Cocoa Touch spans a wide range, from being amazingly easy to make big things happen, to being incredibly complex - enough to MY toes curl (and I have 35+ years of programming experience). Don't let the depth discourage you. Sail your boat on the surface of the ocean and ignore the deep blue sea beneath you. Work on a need-to-know basis and you'll do well.
In the same way that the Space Shuttle zig-zags back and forth as it sets itself up for a perfect landing, that's the way we humans need to operate when we descend into a complex environment. We'll zig-zag back and forth between tutorial books like this, iTunes U videos, formal documentation, sample code, online resources and more. It's also a lot like cleaning a dirty window, and after repeatedly wiping it you'll see more and more clearly.
But starting with an excellent tutorial book like this one FIRST is like using Windex. It's definitely an essential "path of least resistance" toward getting busy and productive with Apple Mac OS/iOS app development. I highly recommend Tim Isted's book!
The Information Workshop