Somewhere I read Philip K. Dick say that the one most important piece of knowledge he had picked up from philosophy is that, "The nature of reality is to disguise its true nature" (which he claimed to have read in Heraclitus, though it's difficult to be sure if Heraclitus actually said that).
TIME OUT OF JOINT is one of Dick's earlier novels that treats the theme of "The World Is Not What We Think It Is" explicitly. It's a novel about knowledge and recognition. The characters play parts in a detective story where the mystery involves piecing together missing parts of the world. Some of the clues include finding light switches on the wrong side of the door, finding a note where a lemonade stand used to be, finding pictures of some actress nobody's ever heard of, and seeing visions.
A number of PKD's later books involved more significant permutations of this theme of Nature-In-Disguise. This story is like a one-trick pony in comparison to books like PALMER ELDRITCH, NOW WAIT FOR LAST YEAR, UBIK, MAN IN THE HIGH CASTLE, MAZE OF DEATH, or VALIS. But the gradual accumulation of evidence, the dawning of recognition in the main characters, makes for pretty fascinating reading.
For good or ill, several modern film makers have really taken this motif to heart (e.g., Dark City, The Matrix, The 13th Floor, The 6th Sense, etc.).