Paul Lockhart is brilliant on the history of guns (and firepower more widely). He is interested not just in the weapons themselves but how they changed the nature of the nation state itself.  Once gunpowder is introduced everything changes. Warfare increasingly becomes something only a powerful state can really afford and a Darwinian competition starts to unfold from the 1500's onwards. Listening to him a lot of developments in history began to make so much more sense to me.

His book Firepower is incredibly readable. It just gallops along. Highly, highly recommended.