Question: How is the character Curley important to the novel as a whole?
Curley is the son of 'The Boss', the owner of the ranch. No one likes Curley – even his wife says 'I don't like Curley. He ain't a nice fella'. She does not seem to love her husband, and it might be that she only goes to the barn where she is killed by Lennie to get away from him. So Curley is important because his unsympathetic character affects his wife and her behaviour, and she is the reason for Lennie's death.
Like a lot of the characters in the novel Curley has a dream, which in his case seems to be a dream of becoming a boxer. This makes him important, because people having dreams is a major theme in the novel. Perhaps his wife was a dream for him once, but in the novel he seems to be worried all the time about where she is and if she is with Slim. He does not seem really to like his wife, and he does not seem to like the ranch hands either. He is therefore important because he shows how bad the life is that the ranch hands lead – even for the Boss's son it is an unhappy life.