If you follow that link, you'll see that the newer ones must be reprints as the author is listed as "John Lee." Unless, I am mistaken that is the same as the one you are getting? Still, not being bale to find an old one is a good sign.

If you really want to know more of value, you could always go to whats it worth to you.com/ and pay for an appraisal.:-) I hope someone here will know more about it, though.