You this will be no surprise once you read the remainder of this review, but I'm going to just say it up front: this book is great. Being a seasoned Xcode user, I can tell you that having this book back when I was first switching over to Xcode would have hugely sped the transition.
The 'Programmer to Programmer' model that Wrox is known for is a an excellent style of reference. There are many benefits of targeting an existing programmer. When writing to an existing programmer there are terms and phrases that the writer can use that programmers will immediately understand, while a newcomer might not. These words and phrases allow the author to communicate to the reader in a rapid, concise and clear way.
The author introduces Xcode by devoting a series of chapters to different sections of the Xcode experience. Each chapter does an excellent job of introducing those little features that you might otherwise miss for a year, and then wonder how you got anything done without it. The chapters are filled with examples and pictures which I believe even a non programmer using the book as their first introduction could follow. I do believe though that a programming book would be a better first book and this book a second. The reason is that even though this book does a great job with simple explanations there are references made to terms which a new programmer wouldn't understand and also a new programmer wouldn't be able to relate to the features without a context. The new programmer says, "That's a great feature, but why and where do I use it?" The existing programmer coming to Xcode says, "Thats a great feature! Kind of like the ---- feature in my old ------ IDE but much more useful for ------."
The author even rounds off the survey of Xcode by addressing the powerful debugging and profiling tools that are included in the Xcode package. One section that I was extremely pleased to find was a section on remote debugging. Remote debugging is a method where one computer is used to run an application and another computer is used to monitor and debug. Remote debugging is a useful feature in general, but I find it indispensable when working on games or other full screen applications that take control of the entire screen. I was pleased to find this section included since I had a difficult time getting it to work the first time I tried to set it up. Again, having this excellent book at my side would have saved me enough time to justify purchasing the book.
I was also pleased with the author's coverage of Shark -?the performance profiling app included in Xcode. I have had wonderful results with using Shark to determine areas of my code that are malfunctioning or just plain poorly written with respect to time efficiency. The book does a wonderful job of explaining the function of usage of all the menu's windows in the application. Another feature that I thought was very useful that fits will with the "Programmer to Programmer" method is the "How it Works" sections that give a good description of why you are doing something, what Xcode is really doing as a result and how it does it.
I think that this book is incredible. I only have one recommendation to someone who's considering purchasing it. Buy it, but also purchase a book that covers the cutting edge Apple made technologies, like Carbon, Cocoa, Foundation, Core Foundation, Core Image, Core Data, Quartz, ect. The reason for this recommendation is that Xcode is built for and integrates well with these technologies and I believe that it would be beneficial to have a book to give an in depth introduction to these technologies, while this book gives an in-depth introduction to the IDE used to develop them. I have not had a chance to examine the book, but it's quite possible that Michael Trent and Drew McCormack's "Mac OS X Programming" also by Wrox is that perfect companion book.