Rangeball-
You may be able to find a copy of Asbel's book on Ebay, which is where I got mine. Don't recall what I paid, but it wasn't very much.
The more I read andfiddle with technique, the more I realize that shooting is like a golf swing. There are basics that are very important, but there are minor variations (grip, anchor point, etc.) that work better for some people. However, like the golf swing, it is crucial to do everything the exact same way each time if one wants consistency.