If we were still in the early nineties then you would probably have a point that being Restricted it should not be in the public view, however although I do not know the contents of this particular book I can make a pretty educated guess, it was probably one of many documents that were overclassified at first publication. So IMO, contents may not be suitable for public viewing but personally I doubt anyone could glean anything from that particular document that isn't already open source.