I have no comments to make on the text, which seems to be of standard quality for this book series, if somewhat short for some species.
The illustrations, however are simply horrible. Not only do most birds look like they have hair, instead of feathers, but in what I can only assume is an effort to make the birds look less "samey", they are twisted around beyond all reason. This is most noticeable in the tails of wrens, which sometimes seem to be distorted to show both the upper and the lower side at the same time, but the artist's skills at painting are not sufficient to pull this off, and the reader is left with having no idea whether what is depicted in the upper or lower side of the tail, at times. You actually feel sorry for some birds (like the female Thrush-like Wren, plate 3, or the Cyprus subspecies of the Winter Wren, plate 13), in which the legs, tail, and body are so twisted that it's hard to even begin to describe what is wrong with the pictures.
Often, it seems the model for these illustrations were birds stuffed with a spatula.
The wing of the Long-billed wren subspecies /bahiae/ (plate 12) appears to have fallen off and been reattached by someone who has never seen a bird before. The same thing is seen in several thrashers. It is quite possible that some of these species occasionally will sit with their wings like that, but it hardly makes the plate comparable, nor useful.
The tails of both Sharpe's Wren and the Fulvous Wren were drawn from individuals that had extremely worn feathers, and many birds are drawn in bizarre poses that obscure more than they reveal. The Chalk-browed Mockingbird (plate 24) is perhaps the most mistreated in this respect, as it is represented by an adult male showing breast and throat, but nothing of the back or top of the head, and which is hidden partially behind a an immature male that is preening itself and also shown in such a way, that nothing of the back or upper side of the wings or tail can be seen. The only other illustration of the species does show these characters, but instead the head is twisted around so that despite the bird being painted from the side, the head is showing mainly the chin. I cannot even begin to understand what possible purpose this illustration could serve.
The most disgraceful plate is that of the Winter Wren (plate 13), however, which is unfortunate, as this is the most widely distributed species in the book, and also one of the most variable ones. Several difference subspecies are purportedly illustrated, but they can hardly be told apart from these illustrations, which are the most amateurish of the whole book. Colours are wrong, birds are twisted around into bizarre and incomparable positions, and the quality of the illustrations are more sketchy than actually painted.
In all, it is a shame that the only available monograph of these groups of birds were illustrated by someone who so obviously either is not able to illustrate birds properly, or couldn't be bothered to do so. It's a shame that the apparent lack of quality control happened in a monograph on groups of birds that are so rich in subtle detail, and can be so hard to tell apart.
The poor quality of the plates would not save this book had it been printed on gold plates and delivered to me by the naked ghost of Darwin.