John Fowles (1926-2005) is considered to be one of the most important metafiction writers in the postmodern age. He broadened the horizon of novel genre by re-illuminating the traditional realism of the novel in the context of postmodern experimental techniques and creative minds. Critiques of his works are generally classified into two categories, one on the themes of the novels and the other on the narrative techniques. Some critics indicate that the protagonist`s struggle for his existential selfhood is prominent in the thematic aspect and that Fowles has established his own peculiar narrative technique. This study examines three masterpieces of Fowles`, The Collector, The Magus, and The French Lieutenant`s Woman, and analyzes his unique narrative technique involved in these novels. Assuming that "space" in the novel, in general, is a medium by which a novelist sets his themes, characters and surroundings in the fictional world, we can find that Fowles notably uses "space" in order to draw the protagonist`s quest for existential authenticity. For that purpose, Fowles uses the ideas of "the realistic space," "fictitious space," and "the boundary" between the two regions, depicting his special interests such as "labyrinth," "tension and surprise," "islands," "mystery," "nature," "exile," and "loss" by means of those three basic terms. Fowles, who has been greatly influenced by a French novelist, Alain-Fournier, represents his idea of mystery in the light of realism. He grants reality and symbolic significance to his fictional texts by fixing actual places and accurate time in his novels. London, Phraxos, and Lyme Regis, the actual names of geographical locations, reveal the theme as well as provide the framework of the narrative structure. They play an important role in the accomplishments of the thematic struggles in the novels, cutting across the limitation of their physical significance. Fowles arranges what he wants to say in the space of fiction. Protagonists in his texts acquire the chance to recognize their existential selfhood, by facing the diverse dimensions of "space" in the novels. The protagonists or the "reader-characters" are driven on a journey to self-realization and experience an ordeal manipulated by the "author-characters" and some mysterious women, their peculiar agents. They, "the many" in Heraclitus`s term, finally select the way to "the few." The protagonists of the novels, who carried out lonesome quests for existential selfhood, show themselves different modes at the end of the journey, crossing over the realistic space, the fictitious space and the boundaries of the two extremely opposite domains. The Collector creates a tragic ending, as the two opposing domains are unable to communicate with each other and the two main characters ultimately remain "the other" to their own antagonists. When returning home, Nicholas in The Magus, though he finally realizes that the fictitious world he experienced in Greece is melted into the realistic world of London, tastes "the loss" because he is now able to understand that the fictitious world, when once lost, is at once irrevocable. Charles, in The French Lieutenant`s Woman, starts a new life at the end of his journey arming himself with the realization that the ultimate answer to his existential quest will never be given and that he himself is the true and the only authentic hero of his own life. Mystery, bearing no reasonable explanation, is the reality itself. Fowles aims to suggest to the readers, by means of his own unique fiction writing, such an authenticity of human life and to present in his fictional world, the protagonists who should go on gripping a tiny knowledge of the existential coordinates in this real world.