The novel tells of earthman John Carter of Mars. A form of astral projection mysteriously transports him to the planet Barsoom, where he encounters both formidable alien creatures resembling the beasts of ancient myth and various humanoids.
As mortals knew him
Carter stood 6'2? tall and had close-cropped black hair and steel-gray eyes. His character and courtesy exemplified the ideals of the antebellum South. A Virginian who served as a captain in the American Civil War, he struck it rich by finding gold in Arizona after the end of hostilities.
While hiding from Apaches in a cave, he found himself mysteriously transported to Mars, where he subsequently had many adventures. The less intense gravity of Mars compared to Earth gave him demigod-like strength.
Mysteriously transported back to Earth, he spent the last years of his life in a small cottage on the Hudson River in New York. He died there on March 4, 1886.
The immortal being
Burroughs portrays John Carter as an immortal being. In the opening pages of A Princess of Mars, the author reveals to the reader that Carter can remember no childhood, having always been a man of about thirty years old. Many generations of families referred to him as "Uncle Jack," but he always lived to see all the members of the families grow old and die, while he remained young. After travelling to Mars, he seemed to find his true calling in life as a warrior-savior of the planet's inhabitants.
His "death" actually represents leaving his inanimate body behind on Earth while he travelled about Mars in an identical body. Carter revealed that he mastered the process of travelling to and from Earth and Mars and could travel between the two at will. Accordingly, his Earth body lies in a special tomb that can only be opened from the inside.
The humanoid "Red Martians", "White Martians", "Yellow Martians" and "Black Martians" resemble Homo sapiens in almost every respect except that they reproduce oviparously. The warlike "Green Martians" have four arms and tusks, and stand approximately four meters tall.
Many Barsoomians generally display warlike and honor-bound characteristics. The technology of the tales runs the gamut from dueling sabers to "radium pistols" and aircraft, with the discovery of powerful ancient devices or research into the development of new ones often forming plot devices. The natives also eschew clothing other than jewelry, providing a stimulating subject for illustrators of the stories.
Domesticated animals include the thoat, the calot and the zitidar.
Although loosely inspired by astronomical speculation of the time, especially that of Percival Lowell, that pictured Mars as a formerly Earthlike world now becoming more inhospitable to life, Burroughs' Barsoom tales never aspired to anything other than exciting escapism.
The tales seem somewhat dated today, but they showed great innovation for the time of writing, and the exciting stories caught the interest of many readers, helping to inspire serious interest in Mars and in space exploration. A Princess of Mars was possibly the first fiction of the 20th century to feature a constructed language; although "Barsoomian" was not particularly developed, it did add verisimilitude to the narrative.
Many later science fiction works, from the Flash Gordon and Buck Rogers films of the 1930s, to Ray Bradbury's The Martian Chronicles, to the Star Wars films, to the Mars trilogy of Kim Stanley Robinson, also offer nods in Burroughs's direction. Robert A. Heinlein's novel The Number of the Beast and Alan Moore's graphic novels of The League of Extraordinary Gentlemen directly reference Barsoom. In L. Sprague de Camp's story "Sir Harold of Zodanga" Barsoom is recast as a parallel world visited by his dimension-hopping hero Harold Shea. De Camp accounts for Burrough's departures from physics or logic by portraying both Burroughs and Carter as having a tendency to exaggerate in their storytelling, and Barsoomian technology as less advanced than usually presented.
The John Carter books enjoyed another wave of popularity in the 1970s, with Vietnam War veterans who said they could identify with Carter, fighting in a war on another planet.