As one example early in the book there are mentions of how many barrels were made and where they were sourced from, and a discussion of barrel iron quality including how horseshoe nails were a highly sought commodity as raw material for barrel forging (especially Spanish barrels). I don't see how the authors anti-gun bias is affecting the historical accuracy of verifiable/collaborated facts. Or who Thomas Ketland was in competition with, and how government contracts for guns were obtained. Or the supposed advantages of Nock's chambered breech patent.
I am skeptical due to probable bias of the author, but I am looking at the factual information it contains, not any conclusions of the author.
As a full professor I rarely pay attention to an author's anyone else's opinions. We professors have a saying "In God we trust, all others bring data."
Regards,
Carl