The Ballantines series came out over 50 years ago. This particular copy was published in 1968.
My Dad collected about 2 dozen volumes of the series and over the years I have looked at but never really read most of them.
Their style is very reminiscent of the contemporary Osprey publishing MAA series which began about the same time.
So over the next little while, I shall be looking at these and seeing how I can adapt the information to my Wargames