Philip K. Dick was one of the most popular science fiction novelists of the 20th century, but the contradictory and wily writer has troubled critics who attempt encompassing explanations of his work. This book examines Dick's writing through the lens of ontological uncertainty, providing a comparative map of his oeuvre, tracing both the interior connections between books and his allusive intertextuality. Topics covered include time travel, alternate worlds, androids and simulacra, finite subjective realities and schizophrenia. Twenty novels are explored in detail, including titles that have received scant critical attention. Some of his most important short stories and two of his realist novels are also examined, providing a general introduction to Dick's body of work.