It is a book for birders of all levels. In origin and concept it is an expanded introduction to the field guide. It covers all of the fundamentals of bird identification with the goal of helping you understand the techniques of birding and the patterns of variation in birds. In that way it will help you get more out of the field guide. A motivated beginner will learn a lot from it, and there is a lot that will also be of interest (if not new) to the experienced birder.