Of Mice and Men is a brief, intense novel. Written to be easily transferred to the stage, it has a play-like sense of drama, as the action builds to the tragic death of Curley's wife and concludes with the wrenching heartbreak of the final scene. Steinbeck's novel is intensely sentimental in its portrayal of Lennie, the simple-minded giant, and George, his friend and protector who is forced to kill him. In fact, its sentimentality has often come under fire, as has the "forced" nature of the plot. The characters seem trapped in a net devised by the author, from which there is no escape. Lennie must kill the woman, just as George must in turn kill him, because everything from foreshadowing to symbolism leads up to that ending.

This deterministic sense of reality, in which people are controlled by unknowable forces, is the novel's central theme. All the characters are intensely lonely and unhappy with their lives (except Slim, a paragon of skill and contentment), yet none of them can escape this unhappiness. Economic and social forces control them, and free will seems illusory. This lack of control over their lives forces them to locate their happiness elsewhere--in Crooks' childhood, or Curley's wife's vision of Hollywood stardom, or George and Lennie's Eden-like dream of their own farm. The whole point of these visions is that they are not real, and Of Mice and Men is essentially the story of how George learns that hard lesson and comes to grip with a life of lost illusions.