The 4th edition of this "Collectors Handbook" is a reprint of earlier editions rather than a much needed rewrite.The background information provided in this book IS very interesting and helpful. HOWEVER, the first question asked on the back of this book is "What is the value of an Audubon Print?" This book answers that question with print by print price information (almost 1/3 of the book) that is over 20 years old. NO price information is even given for the Octavo prints.As a guide for collectors looking for current value information for Audubon prints this book is worthless.