Harry lives in two different worlds. Every time he goes to sleep he wakes up in a different version of reality, in one every person he meets is shallow and safe and pleasant, and in the other they are broken and beaten and filled with bitterness. Harry feels like the happy world is a facade, but that it is more pleasant to live in. Eventually he discovers that he can influence how much time he spends in each world, and that the more time he spends in a world, the more he becomes like that world he becomes.
He has to choose between happiness, the lessening of himself and all he knows, and truth, and the misery that revelation brings.