Gor is an intricately detailed world in terms of flora, fauna, and customs. John Norman — the pen-name of Dr. John Lange, a professor of Philosophy and a classical scholar — often delights in ethnography, populating his planet with the equivalents of Roman, Greek, Native American, Viking, and other cultures. In the novels these various population groups are actually transplants from earth brought there by space-craft through the behind the scenes rulers of Gor, the Priest-Kings, an extraterrestrial species of insectoid appearance. The Gorean humans are permitted advanced architectural and medical skills (including life extension), but are forced to remain primitive in the fields of transportation and weaponry (at approximately the level of Classical Mediterranean civilization) due to restrictions on technology imposed by the Priest-Kings. This limitation is imposed in order to ensure the safety of both the Priest-Kings as well as the other indigenous and transplanted beings on Gor, who would otherwise possibly come to harm due to humans and their belligerent tendencies.
The planet Gor has lower gravity than earth's (which allows for the existence of large flying creatures, and tall towers connected by aerial bridges in the cities), and would have an even lower gravity if not for the technology of the Priest-Kings. The known geography of Gor consists mainly of the western seaboard of a continent which runs from the Arctic in the north to south of the equator, with the Thassa Ocean to the west, and the Voltai mountain range forming an eastern boundary at many latitudes. There are also offshore islands in the ocean, and some relatively sparsely-settled plains to the east of the Voltai. The word "Gor" itself means home stone in the Gorean language (the native language of the city-states in the northern temperate region, and a widely-spoken lingua franca in many other areas).
The series is a planetary romance and the first book, "Tarnsman of Gor," opens with some scenes very reminiscent of the first book of the Barsoom series by Edgar Rice Burroughs, who helped create the genre; both feature the protagonist narrating his adventures after being transported to another world. These parallels end after the first few books, when the stories of the books begin to be structured along a loose plot arc involving the struggles of the city-state of Ar and the island of Cos to control the Vosk river area, as well as the struggles at a higher level between non-human Priest-Kings and Kurii (see below) to control the solar system.
Norman has reportedly completed a 27th book, Prize of Gor, which deals with a rejuvenation serum (going beyond the "stabilization serums" or immortality potions of the other books), and is planning a further book set on one of the "Steel Worlds" (artificial space habitats) of the Kurii.
Most of the books are narrated by transplanted British professor Tarl Cabot, master swordsman, as he engages in adventures involving Priest-Kings, Kurii, and humans alike. Books seven, eleven, nineteen, twenty two, and twenty six are narrated by abducted Earth women who are made slaves. Books fourteen, fifteen and sixteen are narrated by male abductee (and initially slave) Jason Marshall.
The series features several sentient alien races. The most important to the books are the insectoid Priest-Kings and the huge sharp-clawed predatory Kurii, both space-farers from foreign star systems. The Priest-Kings rule Gor as somewhat disinterested custodians, leaving humans to their own affairs as long as they abide by certain restrictions on technology. The Kurii are an aggressive, invasive race with advanced technology (but less so than that of the Priest-Kings) who wish to colonize Gor and Earth. The power of the Priest-Kings is diminished after the "Nest War" described in the third book, and for the most part, Priest-Kings and Kurii struggle against each other only by proxy, through their respective human agents and spies. Some critics have commented that these antipoles — the dispassionate, ultra-rationalist Priest-Kings who find little joy in existence and the Kurii who simply follow their savage instincts and kill in their lack of reflection — are an allegorical appeal to moderate human behavior.
Early entries in the series were mostly plot-driven space opera adventures, with later entries growing more heavily philosophical and sexual. There are many sub-plots that run the course of several books and tie back to the main plotline in later books. Some of these plots start in the first book, but most are underway in the first ten books.
The majority of "known Gor", as the Vosk river region in the temperate north of the continent is often referred to, is reminiscent of ancient Greco-Roman city-states in many respects (aside from the delta city of Port Kar, which is a more anarchic and piratical version of Venice). The most common dating system is Contasta Ar, or years since the founding of Ar (similar to ab urbe condita), and the Viktel Aria road leading to Ar is analogous to the Appian way. In Gor's Torvaldsland, you might think you'd encountered Earth's Vikings. The "Red Savage" peoples of the Barrens are populated with a culture based upon Native Americans, especially the Sioux Nations. The "Wagon Peoples" are a blend of the Mongols and the Gauchos of South America. The Alars appear based on the Alans, barbarians who were later conquered by the Huns. The peoples of the Tahari desert correlate to the nomads of Arabia, the Gorean regions around Schendi to Amazon or Congo River valley populations. The peoples of far north Gor, or the "Red Hunters" as Norman sometimes referred to them, are clearly Inuit — in this case to the point of referring to them as such.
While not officially connected to John Norman's work, Fencer of Minerva is a Japanese animated series containing many of the elements and ideas discused in Gorean Philosophy