A Princess of Mars
Beginning with "A Princess of Mars", Burroughs established a practice which continued in the four sequels of introducing the novel as if a factual account passed on to him personally, wherein John Carter appears as an avuncular figure known to his family for years. The same device appears in several sequels: "The Gods of Mars", "The Chessmen of Mars," "Swords of Mars," and "Llana of Gathol."