I'd guess that a signed copy would get about $40. There are not too many collectors who specialize in signed billiard books, but a signature might double the price of a rarish book. With a little footwork, you could probably get Ray to sign a book. Rosser Reeves' signature will be harder. A dust cover in mint condition will also be tough to find.
The book was reprinted in 2007 with a revised introduction on the occasion of its 30th anniversary. It is also available in Korean. When it was published in 1977, it was the best available info for a wide range of shots. The info has since been greatly extended by other books and articles. Unfortunately, several errors were not corrected in the 2007 reprint.