I've got the book and David Long's, too. From reading them, I'm convinced both authors know what they are doing and "have done it". My biggest complaint is that THEY wrote the books before I did....of course, I never thought of it.
The books are fun and accurate. If you've hunted for long (40+ years for me), there is little there you don't already know. They're still fun to read.
Within the shadows, go quietly.