Answer:
In the first novel, A Princess of Mars, John Carter of Virginia somehow mentally projects himself to the dying planet Mars, known to its various native races as "Barsoom", where he has death-defying adventures, romances the eponymous princess, and saves the world. The novel was a hit, and a series of ten sequels followed over the course of the next few decades, initially chronicling the further adventures of John Carter before shifting their focus to other Martian characters.
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