Unfortunately, like most books on the subject, this isn't going to change any minds. I do respect the work the author went to, getting insight into the NRA via congressional records, but not enough of that comes through in the book, or at least not frequently enough.
There are a few issues where I would imagine the pro-gun people would get upset, because while the author's statements are technically true, they could arguably mislead. It's definitely a book for the anti-gun crowd.
Though most books on this subject are ideological, I can't claim to be completely neutral. For example, when it comes to the historical context of the second amendment, I see the pro-gun side drop quotes like gotchas, frequently from unrelated jurists like George Tucker. Now, I imagine the author of this book is also biased in choice of quotations, but it struck me as a more authentic look at the founding fathers. I mean, James Madison was the writer of the second amendment, so his frequent absence is conspicuous.
My favorite part of the book was a section that felt like just straight journalism: the shift in marketing guns increasingly to the wealthy. Unexpected and not particularly involved in the ideological conflict.