The Lathe of Heaven (1971)

George Orr remembers the world before his dreams changed it, leaving him with an experience others cannot simply verify. His psychiatrist sees an opportunity to improve reality, and the imbalance between them becomes as important as the impossible ability. Le Guin gives the argument the pressure of a psychological thriller. Read it for the question of who is authorised to interpret someone's testimony, particularly when accepting that account would unsettle the listener's own claim to expertise.