I've only had a brief 'flip through' it so far Paul, but in general, it seems OK, with lots of good photos, drawings and diagrams.
It does, however, seem to follow the Nowarra style, of being detailed in parts, but sparse in some areas, with chronology jumping around a bit, and I have some doubts about accuracy in a couple of small areas regarding sub-variants, where again some of the info is sparse or dubious, or both, which I need to cross-reference to establish the true information.
But, allowing for the original publication date (1979), it still serves as a good reference.
I very recently read a magazine review following it's first publication in English, in 1980, when it got good ratings, and for the price, in new condition, I can't grumble.