The swashbuckling pulp hero first appeared in print in 1912, several years before Burroughs' other invention —Tarzan of the Apes—who, thanks to cheaply produced movie serials and TV shows over the decades, is still a household name. While Hollywood has struggled to bring John Carter's adventures to the screen since 1936, it probably didn't help they were set on Mars, with a main character who could leap over tall buildings in a single bound, who fought side-by-side with 15-foot-tall four-armed green men as fleets of giant airships sailed over mile-high cities—or that everyone strode about the strange Martian landscape utterly naked except for their weapons.
It was this fantastic vista that helped fire up the young imaginations of science-fiction authors such as Isaac Asimov, Ray Bradbury and Arthur C. Clarke. Carl Sagan specifically mentioned Barsoom—Burrough's name for Mars—as one of his prime inspirations for eventually pursuing astronomy as a career. Other words from Barsoom's imaginary language will seem familiar to modern ears: Jed (king) and banth are only one letter removed from George Lucas' Jedi and bantha, and he cribbed "Sith" in its entirety.
No coincidence: The tales, originally cliff-hanging short stories in early pulp magazines, had been collected into 11 novels in the 1950s and 1960s when Lucas was growing up. (Princess Leia had nothing on Burroughs' heroine Dejah Thoris, the original pistol-packing princess, and the many fantasy artist depictions of Dejah, clad only in elaborate jewelry, is the direct inspiration for the Leia's infamous metal bikini in Return of the Jedi.)
Propelled along by iconic covers from a young Frank Frazetta, the paperbacks sold millions over the next few decades as part of the exploding genre of "Sword & Sorcery" that included the repackaged collections of Robert E. Howard's Conan the Barbarian and Tolkien's Lord of the Rings.
When Gary Gygax created Dungeons & Dragons with Dave Arneson in the early '70s, he lifted so many elements from the Barsoom books for his game that the Burroughs estate successfully sued the fledgling publisher. While Gygax agreed to remove all of the trademarked material, such as character and creature names, the swashbuckling, princess-rescuing, high-adventure conceits remained. D&D has been played by millions over the past 40 years, and is widely cited as the strata on which modern video games are built.
Marvel Comics published a popular comic book adaptation in the late '70s that introduced another generation to the world Burroughs imagined. Thrice since then have comic book publishers tackled Barsoom, including, most recently, a small imprint that is currently showing John Carter and Dejah Thoris as Edgar Rice Burroughs intended—naked—and is involved in yet another lawsuit with the ERB estate.
In an odd twist that has become an object lesson in copyright, Burroughs' family controls a few trademarks related to the property, but not the early novels themselves, which are now in the public domain. While a conundrum for the courts, it is a boon for readers: you can currently read the first volume, "Princess of Mars," on the Library of Congress site for free.