We live in an age of general editorial negligence, it seems, and of course most buyers of a book like this will be chiefly interested in the pictures, but still, when a publisher promises "authoritative text by leading firearms experts", someone really should look the whole thing over attentively before it goes into print.
Just flipping through, I notice that the authors seem to think that Costa Rica is a Caribbean island (page 356). A bit further on (page 361), it is claimed that "since 1870, Paraguay has been at peace with her neighbours." Oh really? What about the Gran Chaco war with Bolivia (1932-1935), in which 36.000 Paraguayan soldiers died?
Regarding firearms history specifically, there clearly are important gaps in the authors' collective knowledge. For instance, it is repeatedly (pages 380, 455) stated that in modern times, the Netherlands never manufactured their own military small arms (apart from a short run of AR-10 rifles in 1959-1962 for export). In reality, in the period up to WW II, the Dutch Artillerie Inrichtingen produced, among many other things, roughly half a million Mannlicher rifles and carbines, and many thousands of machine guns of various models.
What I find really disturbing is that four British experts together are apparently unable to correctly identify a Webley Mark VI revolver (page 59 - in fact, it's a picture of a much earlier model). Switched captions are of course the bane of firearms books, and this one is no exception: S&W Models 36 and 19 (pages 119-120) for example. And Bulgarian AKs are allegedly made by FÉG in Budapest.
Finally, while the other directories are limited to military arms, in the handgun section there are many guns which have never seen military service and never will, at least not as standard issue handguns; I have no real objection to that, but why on earth is so much space devoted to Para-Ordnance? No less than twenty-six variants of the same basic model are shown, while many handgun manufacturers who have been around much longer and have produced a much larger variety of guns get much less attention. The authors are certainly laying themselves open to suspicions of commercial interest here.