MisterHappy,
Ron Glidden has made it his job to understand the convoluted MA gun laws like nobody else in MA, at least since 1998 when I met him at one of the first lectures he gave to LEOs on the then new law.
His credibility is based on his constant communication with the authors of those laws (yes he used to talk with Queen Cheryl, her staff attorneys, and "side of beef" - her chief of staff . . . they were largely the authors of what we live with today), EOPS Legal Dept., etc. When a question is raised, Ron researches the answer and provides it with an air of authority.
Many others merely tell you what they wish the law was, without putting the research into it to vet the info. I don't always agree with Ron, but I greatly respect his efforts to attempt to make it more understandable.
He also teaches this to new recruits. The value in his book are in the notes which describe things in more down-to-earth words.