I've been developing iOS apps for 3+ years and got enormous value from this book. This is NOT a hand-holding step-by-step of creating your first app, like so many (too many?) books out there.
This is more like a peek inside the toolbox of a highly successful app marketer. You do get info on the overall process of researching app ideas, outsourcing development, marketing your apps, etc. but rather than long-winded abstract discussion, the author instead provides a stockpile of links, suggestions, and recommendations for doing it right.
By all means, pick up the step-by-step howto manuals too. Those will help you get through the process of creating your first app. But if you're already in the business, or you want to ensure you can build a big family of successful revenue-generating mobile apps, this book is absolutely essential reading.