As a relatively inexperienced Birdwatcher I have tried (with varying success) to find a good field guide - generally speaking the Collins guide (Mullarney, Svensson et al) is by far the best as far as a very high quality book with a standard approach goes; however this book is something which I think is quite unique. Firstly by identifying different behaviours it allows you to search for that unknown bird in a very different way, secondly instead of stumbling around different plumages, it actively encourages you to look at what the bird is doing. As a very, very amateur photographer I know it is all too easy to look but not see. By concentrating on how the bird is behaving (IN ADDITION to usual plumage, markings etc.) this book encourages much more active birdwatching. I would say that alone the book probably is not sufficient but it makes that clear from the outset. A fantastic book that I recommend utterly - I'm certain experienced and inexperienced birdwatchers alike can take something from this.
Full of info you wouldn't find in most bird books. I have coveted this book for some time. Behaviour has often been overlooked in the past and this is a welcome addition to the usual identification guides.