Too late to make a killing on your book. It's back in print with more (color!) pictures and more pages.
"Kindig defines the American Longrifle as the finest example of truly American rococo art, using 262 rifles from his extensive collection. The most comprehensive source ever published, this monumental 3rd Edition features dramatically improved photos using the original negatives, now including the locks. A new 48 page addition features over 240 full color photos with multiple, detailed views of 28 of the finest rifles, many previously unpublished. Much new information discovered over the last 35 years has been added, along with the extensive information & photos from the 1983 edition. The early Pennsylvania & Maryland schools of gunsmithing are covered, along with biographical data on the makers, 624 pages and over 1,100 photos & illustrations, 240 in full color.
Annotated third edition by Joe Kindig, Jr. - (2017) - Hardcover"
https://www.shumwaypublisher.com/shop/item.aspx?itemid=45