Why don't you e-mail Barnes and Noble, ask what their position is on customers entering their stores with open, loaded weapons. My guess, they are against it, and so is the insurance company that writes their policy. Hey wait a minute, I'm going out on a limb here, but I'm going to guess they don't want any loaded weapons on their premisis , concealed or not!
If they did not wish weapons on their premises, they could post a sign. The fact that they have not, and that the general manager of the store personally told me that they do not wish to bar those who lawfully carry firearms, suggests otherwise.