In LeGuin's "The Ones Who Walk Away from Omelas," the narrator seems to feel the need to intrude and offer explanations in the narrative. For instance, regarding happiness, while the narrator has described the "cheerful faint sweetness of the air" and the "great joyous clanging of the bells," she feels the need to state,
Joyous! How is one to tell about joy? How describe the citizens of Omelas?
They were not simple folk, you see, though they were happy. But we do not say the words of cheer much any more. All smiles have become archaic.
Later, she exclaims,
O miracle! but I wish I could describe it [the society] better. I wish I could convince you...Happiness is based on a just discrimination of what is necessary, what is neither necessary nor destructive, and what is destructive.
This ambiguity of the definition of happiness is also present in the expression of mood and morals. With reference to mood, the narrator states, "As you like it." Then, regarding morals, she states,
One thing I know there is none of in Omelas is guilt.
Yet, there are those who walk away from Omelas after they learn of the suffering child.
So---perhaps, your thesis could focus on the ambiguity of any true happiness, real mood, or true morals. With a narrator intruding in order to convince the reader of things, there are certainly some questions as to the utopian state of Omelas. (By the way, the title means "Man, alas.") After all, if a narrator must convince the reader, do these qualities really exist?
Your essay can help the readers decide.