I know you asked about the inner workings of firearms, and these two books are not about that, nevertheless, are good coffee table books. Easy to read, lots of visuals, and certainly related, though not specifically what you asked for. The books are must reads imo. a ggood handgun shooting book is "Practical Shooting-Beyond Fundemenatals" by Brian Enos. The rifle book is "The Art of the Rifle" by Jeff Cooper.