Other reviewers have given this guide an excellent detailed thumbs up, I see no point in repeating at length. It's greatest strength is its size - it IS pocket sized. Any guide to be used outdoors, HAS to be a compromise. Yes, as a serious birder, I have many books, all the usual suspects, Peterson, Collins, Philips etc etc etc! All in their own right great publications, only 'let down' by their dubious portability. If your birding sees you on the move, with 'scope tripod & binos and other paraphernalia, weight is a premium, so this is your book. Yes!
P.S: Their is a paperback version available - lighter still.