Doubt this was ever a hard back or bestseller. My recollection is that I got it in the early to mid-70s. I recall that it had something to do with a priestly group of "extrapolators" who could manipulate all sorts of things with their minds. In fact, the single outstanding aspect of the book was the frequent use of the word extrapolate and its derivatives. Not sure of the publisher, but it may have been Ace.