Any book by Jack O'Connor--admittedly mostly about long guns vs handguns (but the likes of Taffin and Keith alredy mention will cover you pretty well on pistols). O'Connor wrote at least a few books. One in particular come to mind "Complete Book of Rifles and Shotguns," but he also has a few others independently on rifles and shotguns. Great reads. Hard to find in original printings, I imagine some have been redone. Jack's been gone awhile now, but so has Keith, etc., but they all cover 95% of what's been important over the years.
Also, along the lines of a more generic, lower priced coffee table picture book "The Illustrated Book of Guns" edited by David Miller.