I personally love this book. However, another review about the ridiculousness of some of the suggestions in the book, like "sleep on the other side", "do the dishes", etc, has opened my mind up to a caveat that probably should have been written somewhere on the cover of this book.
In order to really appreciate and benefit from this book, you must be a curious AND contemplative person by habit, and ideally, you need to be looking for something but you don't know what it is exactly just yet. Actually I am inclinded to say that it is a requirement before buying this book, that you are looking for something unknown.
I think it is actually an admirable type of people who may not like this book; they're probably well disciplined people who can straightforwardly use procedures or steps that lead to known, specific results. They're people who know exactly what they want, exactly what they enjoy, and have minimal trouble persevering with the steps necessary to achieve their desired results. If you're like this, then I personally think this book is of no use to you. You're better off buying a scientific or instructional book that explains to you how exactly you can achieve something specific.
On the other hand, if you're the dreamy, contemplative, curious, fickle, quickly-bored, creative, adventurous, explorative, yet lost type of person, then my guess is that you'll love this book.
My own summary of the need that this book may fill is to read it if you are looking for something and you don't know what it is, whether you need to do this for work to come up with new creative ideas or for life to find your life's purpose. But it is not enough by itself; it is just a great addition to the friendly help you can get along the way.