Loneliness
Lonliness is a major theme throughout the book. In fact in the book we immediatly see how Lennie and George traveling together is strange. When George starts to tell Lennie about the farm they're going to own he starts out with "Guys like us, that work on ranches, are the loneliest guys in the world. They got no family. They don't belong no place. They come to a ranch an' work up a stake and then they go inta town and blow their stake, and the first thing you know they're poundin' their tail on some other ranch. They aint got nothing to look ahead to. (Pg. 15)" This shows that, mostly, in this time men were lonely. They travled alone and didn't trust anyone. The lonliness does get to the men though as Slim and George say; "I ain't got no people," George said. "I seen the guys that go around on the ranches alone. That ain't no good. They don't have no fun after a long time they get mean. They get wantin' to fight all the time." "Yeah they get mean," Slim agreed. They get so they don't want to talk to nobody. (Pg 40-41)" Another example of lonliness as a theme is Crooks. Crooks is a man who is forcibly isolated since he's black and he pushes everyone away. Because of this he sucumbs to the lonliness and becomes a bit mean. You can also see this with Curley who only has his wife who avoids him and finds it strange for two men to work together as you can see when he says "Oh, so it's that way. (Pg. 26)" after George tells him that him and Lennie travel together.
Friendship
Right away the story opens with the lonliness of the men of this time but for George and Lennie this isn't an issue since they have eachother. When George tells about their mutual dream he always starts by talking about how ranch hands don't have family or anyone to look after them but he always follows up with "With us it ain't like that. We got a future. We got somebody to talk to that gives damn about us. We don't have to sit no bar room blowin' in our jack jus' because we got no place else to go. If them other guys gets in jail they can rot for all anybody gives a damn. But not us. (Pg. 15)" and Lennie finishes with "But not us! An' why? Becauses.. because I got you to look after me and you got me to look after you, and that's why. (Pg. 15)" While George and Lennie can be seen as inequal they care about eachother, and they still somehow manage to be friends. They are practically the only men with true friends in the entire book. All the other men could leave whenever they want and then have no friends afterwards but George and Lennie stick together for as long as possible.
Dreams
Yet another important theme to this book is dreaming, specifically, for George and Lennie, the American Dream. They both live with the American dream dictating their life. Lennie asks George constantly to tell him about the ranch they're going to own. George always complies by telling him, "O.K Someday-we're gonna get the jack together and we're gonna have a llittle house and a couple of acres an' a cow and some pigs (Pg. 15)" and "We'll have a big vegetable patch and a rabbit hutch and chickens. And when it rains in th ewinter we'll say the hell to goin' to work and we'll build up a fire in the stove and set aroundit an' listen to the rain comin' down on the roof. (Pg. 15)" Despite Lennie not knowing much he always knows about the ranch contributing to George's story by always saying "An' live off the fatta the lan' (Pg. 15)" and mentioning the rabbits he wishes to care for. George and Lennies dreams are what motivate them. The dream motivates George to stay with Lennie and work while the dream motivates Lennie to try and behave. All Lennie wants is to own and tend some rabbits and all George wants is his own land where he doesn't have to listen to anyone but himself. Dreaming is a very important concept for this book.