We already know Crooks reads often, but there is another important possession here: his gun. As we know, Crooks is black, older, and injured. So, he might feel the need to have something to protect himself at all times. Although, I don't think it's unusual to have a gun if you are on a ranch. But, I think that the gun in Crooks' room holds significance. A significant part of Crooks' environment is the nail on the wall holding his glasses. Normally, people wouldn't really want to put glasses on a nail/wall because they could get scratched there. But, I think that Crooks' hangs his glasses above his bed with a nail so that he doesn't have to bend down to get them (which would hurt his back). So, even though Crooks is injured, the people in his workplace obviously don't care. If they did, they may have given him something better than a nail. Basically, the nail shows that many people don't care/try to accommodate for Crooks' injury.