what mood does the setting establish

There is a definite sense/tone of isolation and estrangement from Holden's society of prep schools and social conformity. There is something human about his experience that may well teach us something about not living badly. Holden indicates that he has to “take it easy” at a new place, strongly implying that he now is receiving psychiatric or psychological help. The details in the first chapter already indicate that he has pursued an aimless, self-destructive path. Expelled from school for failing several classes, Holden essentially describes himself as a perpetual failure. Even worse, in his failings he appears to have a strong disregard for others. His solipsistic self-destruction makes him unable to grasp the consequences of his actions, such as when he chooses humor and argues that he somehow is not responsible after he loses the fencing equipment on the trip to New York.