I have a 10 year old copy of McKeown's that I got for a few quid from a 2nd hand bookshop. I've found that generally the relative prices of collectable cameras has remained reasonably consistent, so if I can find the current market price of camera A I've got a good idea of what camera B is likely to be worth. Also the 1997 dollar numbers are similar to the current Great British Pound numbers (that is, 200 USD in 1997 = about 200 GBP today).
It's also fun just to browse through it.
In summary, my opinion is that it can be a useful book, but probably not worth the money if bought new today.