How many Edgar Rice Burrough’s books in Barsoom were there?
The first three are the absolute best.
A Princess of Mars.
The Gods of Mars.
Warlord of Mars.
After that the stories leave John Carter behind (he is the hero perfected) in order to tell more classic stories of the heroic ideal being achieved by lesser characters - first his son “Carthoris” romancing the titular princess in the 4th book....
Thuvia Maid of Mars.
Chessmen of Mars (about the romance of John Carter's daughter Tara of Helium by a new hero, Gahan of Gathol).
The Mastermind of Mars (new hero from Earth, Ulysses Paxton)
A Fighting Man of Mars (new hero Hadron of Hastur, relative of the husband of Tara of Helium).
Swords of Mars (back to John Carter, fighting a league of assassins!!!)
Synthetic Men of Mars (new hero Vor Daj)
Llana of Gathol (about John Carter's granddaughter)
John Carter of Mars (back to John Carter again).