I think that the first chapter is fairly important in Steinbeck's novella. Its basic elements are present in the opening. The introduction of the Salinas Valley will prove to be important at the end of the novel, and it is something we see here. The most important elements out of the first chapter would be the full introduction of Lennie and George. There is much present between them that helps to establish how both are seen throughout the novel. The fact that Lennie depends on George and how George is the "brains" between them is extremely important. In something as small as Lennie drinking water from the pond or in how Lennie imitates George and how he lies down are both reflective of this. At the same time, the dialogue between them helps to bring out repetitive themes or ideas that will present themselves repeatedly in the course of the novel. The dream that both men share of owning their own farm is something seen, something that will come to occupy so much importance between them. Also, the fact that George gets angry at Lennie, who for his part pretends to leave if that alleviates George's tension. These elements are brought out in the first chapter.