I've always been reluctant to answer this because it seems better to buy direct from the author himself, as I did at Expo. BUT if he is too busy or otherwise unable to respond, go to Amazon - he still gets a sale, but not as good as a direct sale I imagine.
The first three vols can be bought individually for less than US $40, all together for US $108.51, the latest EM one is US $65, add some postage to this and I have found delivery to be about a week. I bought "The Complete Pinball Book" by Marco Rossignoli from Amazon which is a good book too - lots of good pictures and talks about machines and how they developed over time.
