I hesitated quite a while before purchasing this book. Afterall, I already owned "Butterflies Through Binoculars" and the Kaufmann Butterfly Field Guide (really great books), as well as the Audubon Society and Peterson butterfly field guides (very good books), so why should I buy yet another one? How could they possibly contain more useful information than what the other books posessed? Well, I was swayed by the other Amazon reviews, bought the book, and am very happy that I did. This book contains lots of information not available in the others, including more detailed ecological, behavioral, range, and regional differences information. The range maps are far more detailed than range maps included in the other guides. Even Skippers are given in-depth treatment. The photographs are marvelous. The book is aptly subtitled "An Observer's Guide," rather than classified as a "field guide." The book is too bulky to be an ideal field reference, and the text and illustrations do not emphasize field identification over ecology. The book could serve adequately as a field guide, but ideally one would own both a field guide for carrying in one's back pack, and this book for more in-depth reading at home. As with the other butterfly field guides mentioned above, this book does not provide many illustrations of butterfly larvae, but just recently two excellent caterpillar books have been published and are available through Amazon, "Caterpillars in the Field and Garden: A field guide to the butterfly caterpillars of North America," and "Caterpillars of Eastern North America" (fabulous coverage of moth, as well as butterfly, caterpillars). But Butterflies of the East Coast contains a wealth of other information not included in the other field guides, and I heartily recommend purchasing this book to supplement whatever field guide you may already posess, it should greatly enhance your pleasure in observing butterflies.