It features John Carter, a late-19th-century American Confederate veteran who is mysteriously transported from Earth to the dying world of Mars where he meets and romances the beautiful Martian princess Dejah Thoris.

[4]: 95–101 Most of the Barsoom books are novels, but two are collections of shorter works: Llana of Gathol has four linked novelettes, originally published in Amazing Stories during 1941,[8]: 664  and John Carter of Mars is composed of two novellas.

[citation needed] 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.

[9]: 147  They mostly take place on the surface of an alien world, frequently include sword fighting, monsters, supernatural elements such as telepathic abilities, and civilizations similar to Earth in pre-technological eras, particularly with the inclusion of dynastic or religious social structures.

[7]: 1210 Like most of Burroughs' fiction, the novels in the series are mostly travelogues, feature copious violence, and often depict civilized heroes captured by uncivilized cultures and mimicking their captors to survive.

[11]: 93–94 Most Barsoom novels follow a familiar plot structure wherein a hero is forced to a far-off location in search of a woman kidnapped by an odious but powerful villain.

[12]: 27–28 While Burroughs' Barsoom tales never aspired to anything other than escapism, his vision of Mars was loosely inspired by astronomical speculation of the time, especially that of Percival Lowell, that saw the planet as a formerly Earthlike world now becoming less hospitable to life due to its advanced age.

During the time Burroughs wrote his first Barsoom stories, the theory was put forward by a number of prominent scientists, notably Lowell, that these were huge engineering works constructed by an intelligent race.

All Barsoomian races resemble Homo sapiens in most respects, except for being oviparous[9]: 148  (making them classified as monotremes instead) and having lifespans in excess of 1,000 years (though actual life expectancy is far shorter.

Tars Tarkas, who befriends John Carter when he first arrives on Barsoom, is an unusual exception from the typical ruthless Green Martian, due to having known the love of his own mate and daughter.

Air travel over the barrier is discouraged through the use of a great magnetic pillar called "The Guardian of the North," which draws fliers of all sizes inexorably to their doom as they collide with the massive structure.

This is the destination of the River Iss, on whose currents most Martians eventually travel, on a pilgrimage seeking final paradise, once tired of life or reaching 1000 years of age.

When they reach the age of 1000 years they make a pilgrimage to the Temple of Issus, unaware that they have been manipulated into doing so in order to be slaughtered by the Black Men of Mars in an analogous deception to that the Therns practice on other Martians.

[4]: 97 The Chessmen of Mars introduces the Kaldanes of the region Bantoom, whose form is almost all head but for six spiderlike legs and a pair of chelae, and whose racial goal is to evolve even further towards pure intellect and away from bodily existence.

In addition to the naturally occurring races of Barsoom, Burroughs described the Hormads, artificial men created by the scientist Ras Thavas as slaves, workers, warriors, etc.

Although the Hormads were generally recognizable as humanoid, the process was far from perfect, and generated monstrosities ranging from the occasional misplaced nose or eyeball to "a great mass of living flesh with an eye somewhere and a single hand.

The mysterious Yellow Martians, who live in secret glass-domed cities at the poles and appear in The Warlord of Mars, have a form of magnet which allows them to attract flying craft and cause them to crash.

Scientist Phor Tak, who appears in A Fighting Man of Mars, has developed a disintegrator ray, and also a paste which renders vehicles such as fliers impervious to its effects.

In The Master Mind of Mars aging genius Ras Thavas has perfected the means of transplanting organs, limbs and brains, which during his experiments he swaps between animals and humanoids, men and women and young and old.

[4]: 95–101  Later, in Synthetic Men of Mars, he discovers the secret of life, and creates an army of artificial servants and warriors grown in giant vats filled with organic tissue.

Tara of Helium compares them to effete intellectuals from her home city, with a self-important sense of superiority; and Gahan of Gathol muses that it might be better to find a balance between the intellect and bodily passions.

This is punctuated by the fact that the Therns and First-Born are obliged to create strongholds in the south polar regions, to insulate themselves from the remainder of the planet dominated primarily by red and green Martians.

[27] In 1895 Lowell published a book titled Mars which speculated about an arid, dying landscape, whose inhabitants had been forced to build canals thousands of miles long to bring water from the polar caps (now known to be mostly frozen carbon dioxide or "dry ice") to irrigate the remaining arable land.

Wells' novel, The War of the Worlds, most definitely influenced by Lowell and published in 1898, did however create the precedent for a number of enduring Martian tropes in science fiction writing.

These include Mars being an ancient world, nearing the end of its life; being the home of a superior civilization, capable of advanced feats of science and engineering; and a source of invasion forces, keen to conquer the Earth.

[29] Notable fans of the Barsoom series include Carl Sagan, Terry Wilcutt, Jane Goodall, Michael Crichton, Arthur C. Clarke, and Ronald Reagan.

[17]: 239–249 [33] The Warriors of Mars rules for miniature warfare by Gary Gygax and Brian Blume were controversial, and a legal dispute with the owners of the rights to the Barsoom series led to withdrawal of this title from the market.

In addition, Leigh Brackett, Ray Bradbury, Andre Norton, Marion Zimmer Bradley, and Alan Dean Foster show Burroughs' influence in their development of alien cultures and worlds.

In the first chapters of Gore Vidal's novel Washington, D.C., the character Peter Sanford – sixteen at the outset of the plot – indulges in vivid and detailed fantasies of being John Carter, and adds explicit erotic scenes not appearing in the original Burroughs books.

From October 16, 1994, to August 13, 1995, writer Don Kraar and artist Gray Morrow set an arc first in Pellucidar and then on Barsoom featuring Tarzan, David Innes, and John Carter in a crossover adventure through their respective worlds.