This is certainly the best parrot guide I've ever seen, the result of a great deal of expertise and talent. The illustrations are clear, and for many species the bird is shown from the top and bottom to aid identification. Where birds vary in appearance by sex this is shown, and in most cases it seems the different subspecies are shown as well. This is particularly pleasing in the case of the Rainbow Lorikeet, the multiple highly variable subspecies of which are treated over six pages (including three plates). Similar looking species are lumped together and the illustration quality makes it clear what to look for to tell them apart. The maps are generallly good with each map using separate colours to mark the separate ranges of the subspecies.
There are, unfortunately, flaws. The common names used follow earlier editions, with a seeming preference for avicultural names over those used by birdwatchers and the various ornithological organisations. While this is the perogative of the writers, it would have been helpful to include commonly used alternatives either in the text or in the index. Additionally the taxonomy used seems somewhat out of date for a book just published. It's been ten years since Boon (2001) showed that the Norfolk and New Caledonian Parakeets were not only distinct from the Red-fronted Parakeet (actually the Red-crowned Parakeet, but never mind) but actually basal to the entire genus, yet they are still lumped in that species in this new edition. Similarly the Chatham Parakeet should be treated as very distinct from the Yellow-crowned Parakeet, but isn't. In some instances these splits are alluded to in the text (as they are for the Chathams Parakeet), but this isn't consistently done (for example in the case of teh Ouvea Parakeet from the Horned Parakeet).
These are essentially niggles. The problem with these kinds of work is that the closer you get to perfection the more glaring these small problems become. This is still an excellent book that I don't regret purchasing.