how does john steinbeck create a memorable climax in Of mice and Men

As soon as Curley's wife enters the barn with Lennie, the reader knows things are going to go wrong. The tension ramps up as Curley's wife flirts with a clueless Lennie. After Lennie inadvertently kills her, the novel progresses to the end in classic Steinbeck style. The final scene is heart wrenching. It is a climax to a relationship that, for some reason, seemed inevitable. George must do the kindest thing he can. George turns Lennie around and tells the same story of comfort we have heard many times over,

"Go on said Lennie, George raised his gun and his hand shook...."