One of the main themes is friendship. George and Lennie have a complex friendship where George looks after Lennie. Another theme is the American Dream. They both dream of having their own piece of land, which represents the hope and aspiration that many had during that time. Also, loneliness is a theme as many of the characters in the novel are alone in some way, like Crooks who is isolated because of his race.
One of the main themes is friendship. George and Lennie have a complex friendship where George looks after Lennie. Another theme is the American Dream. They both have a dream of having their own land, which represents the hope and aspiration that many had during that time.
There's also Curley, the boss's son. He is a small - statured man with a big temper. He is jealous and aggressive, especially when it comes to his wife. His wife is another important character. She is lonely and often flirts with the ranch hands, which causes a lot of tension on the ranch.
The main theme is the futility of the American Dream. Lennie and George have a simple dream of having their own land, but various factors like poverty, discrimination, and human nature itself work against them, ultimately leading to their downfall.