Massad Ayoob’s In the Gravest Extreme, though getting old at this point, and some parts a little outdated, is still quite useful. He spends quite a bit of time exploring the issue of mindset, whether you are ready and willing to actually use that firearm in the gravest extreme. Worth it just for those parts, but there are other parts to recommend it. In fact, I did recently.
A worthwhile book. Been decades since I read it, but I did re-read passages recently.