It is always the dream of the powerless to have a little land where they can make their own decisions and be their own bosses. In this case, having their own place would ease the loneliness and put a damper on Candy's fear that he'll be turned out when he's too old to work, Crooks' fear he'll be gone because of his race and bad back, and George and Lennie's desire to be free of the boss and do what their hearts desire. But Crooks certainly tells the reality of the story in one of the most poignant speeches in the novel: "Just like heaven. Ever'body wants a little piece of lan'. I read plenty of books out here. Nobody never gets to heaven, and nobody gets no land. It's just in their head. They're all the time talkin' about it, but it's jus' in their head." This speech foreshadows George's plight at the end of the book.
California civil code a book of civil law for the state of California.
aloof distant in sympathy, interest, etc.; reserved and cool.
meager of poor quality or small amount; not full or rich.
took a powder [Slang] ran away; left.
booby hatch [Slang] an institution for the mentally ill.
nail keg a barrel for holding nails.
"roll your hoop" a reference to a child's game. Candy is saying Curley's wife is just a child.