John Steinbeck was a good fiction writer. He knew that a story has to be dramatic in order to be interesting. Drama is always caused by conflict and nothing but conflict. In a story such as Of Mice and Men there is a big, ongoing conflict involving the struggle for survival. But it will be observed that each scene has its own minor conflict. This is no accident. Steinbeck knew that a scene could only be interesting if it was dramatic, and it could only be dramatic if there was conflict. So when George is first meeting with Candy in the bunkroom and getting acquainted, Steinbeck creates a conflict about the bunk. George suspects that it is infested with bedbugs or crab lice, and Candy tries to assure him that it is perfectly clean. Candy is defensive because the cleanliness of the bunkhouse is his responsibility. A simple scene in which two guys move into the bunkhouse is thereby enlivened with a bit of gratuitous conflict.
It is interesting to check every scene in this novella to see if the author has introduced some drama through conflict. For example, when the boss comes in to interview George and Lennie he immediately becomes suspicious because George does all the talking.
The boss deliberately put the little book in his pocket. He hooked his thumbs in his belt and squinted one eye nearly closed. "Say--what you sellin'?"
"I said what stake you got in this guy? You takin' his pay away from him?"
"No, 'course I ain't. Why ya think I'm sellin' him out?"
This goes on for some time. Then George turns on Lennie and berates him for not keeping his mouth shut.
Steinbeck invents conflicts throughout the story. For example, there is a serious conflict between Curley and Lennie. There is a conflict between Candy and Carlson when Carlson wants to shoot Candy's old dog. There is a lot of conflict in the scene in Crooks room when Lennie, Candy, and Curley's wife all intrude. Slim even suggests there will be a conflict in the room where the men eat.
"You guys better come on while they's still something to eat. Won't be nothing left in a couple of minutes."
There are even references to a conflict which occurred in the past in the town of Weed. George describes the incident twice--once to Lennie and a second time to Slim. George is having a conflict with Lennie at the campsite when he brings up the conflict in Weed--a conflict within a conflict.
Curley and his young wife have an ongoing conflict up until the time she is found dead in the barn. He keeps chasing after her and she keeps trying to get away from him.
All of these conflicts are "realistic." But the intention is to hold the interest of the reader or the future theater audience by creating one dramatic situation after another.