Foreshadowing the cyberpunk sub-genre, Dick brought the anomic world of California to many of his works, exploring sociological and political themes in his early novels and stories while his later work tackled drugs and theology, drawing upon his own life experiences in novels like A Scanner Darkly and VALIS. Alternate universes and simulacra were common plot devices, with fictional worlds inhabited by common working people, rather than galactic elites. "There are no heroics in Dick's books," Ursula K. Le Guin wrote, "but there are heroes. One is reminded of Dickens: what counts is the honesty, constancy, kindness and patience of ordinary people."

His novel, The Man in the High Castle, bridged the genres of alternative history and science fiction, resulting in a Hugo Award for Best Novel in 1963. Flow My Tears, The Policeman Said, a novel about a celebrity who wakes up in a parallel universe where he is completely unknown, won the John W. Campbell Memorial Award for best novel in 1975. In these stories, Dick wrote about people he loved, placing them in fictional worlds where he questioned the reality of ideas and institutions. "In my writing I even question the universe; I wonder out loud if it is real, and I wonder out loud if all of us are real," Dick wrote.

Dick's stories often descend into seemingly surreal fantasies, with characters discovering that their everyday world is an illusion, emanating either from external entities or from the vicissitudes of an unreliable narrator. "All of his work starts with the basic assumption that there cannot be one, single, objective reality," Charles Platt writes. "Everything is a matter of perception. The ground is liable to shift under your feet. A protagonist may find himself living out another person's dream, or he may enter a drug-induced state that actually makes better sense than the real world, or he may cross into a different universe completely."