The Focal Press guide to the Retina cameras, by W.D. Emanuel, in its several editions, is quite handy, as Chris already pointed out, but - at least judging from my experience - it isn't the easiest book to come by in the large series of manuals once published by Focal Press. If you want a broad model coverage, the later editions are preferrable.
In case you live in the US, it might be easier to find the Amphoto edition of W.D. Emanuel Retina Guide; Amphoto Focal Book was an imprint of the American Photographic Book Co., based in N.Y. The second edition was published in 1958; I suppose it must be more plentiful than any of the Focal Press successive editions released in the UK during the 1950s.
Alex
Edit: sorry, now I noticed you live in NZ.