'Dune: Prophecy' is based on a book — but not one written by 'Dune' author Frank Herbert

• "Dune: Prophecy" is a prequel series set in Frank Herbert's "Dune" universe.
• The story is based both on "Dune" and the prequel novel "Sisterhood of Dune."

If you spent a good chunk of Denis Villeneuve's "Dune" films morbidly curious about the shady Bene Gesserit, you weren't the only one — so was Warner Bros.

Before the company behind HBO became Warner Bros. Discovery after a merger, it started development on a "Dune" prequel series focused on the politically savvy, supernaturally powered sect of women. After some staffing changes during the development process, a retitle, and a shift to air on the company's flagship cable channel HBO, we're finally left with "Dune: Prophecy."

The series takes place 10,000 years before the birth of Paul Atreides (played by Timothée Chalamet in Villeneuve's films) and shortly after an event known as the Butlerian Jihad (when humans rose up against, defeated, and ultimately banned thinking machines). It hones in on the origins of the Bene Gesserit, known at the time as the Sisterhood, and the political machinations of a young Empire.

If you're a true "Dune" fan who's read at least some of the franchise's auxiliary novels, this history should be vaguely familiar. "Dune: Prophecy" is partly based on Frank Herbert's seminal science fiction work and on "Sisterhood of Dune," a novel written by Herbert's son Brian Herbert and sci-fi author Kevin J. Anderson.

'Sisterhood of Dune' is a prequel novel set in the 'Dune' universe

Frank Herbert's "Dune" novels compose only a small part of the franchise. Following his death in 1986, his son Brian and Anderson began publishing "Dune" prequel novels in 1999.

"Sisterhood of Dune" is part of the "Great Schools of Dune" prequel series written by the two, and it was published in 2012. It's set 83 years after humanity's victory over the thinking machines, and as the title suggests, covers the early days of the Sisterhood.

After Raquella Berto-Anirul survives a poisoning that unlocks her genetic memory, she becomes the first Reverend Mother. That process, dubbed the Spice Agony, killed a number of sisters who were unable to withstand the poison — but it eventually turned others into Reverend Mothers themselves.

Raquella trains Valya, a daughter of the war-disgraced Harkonnen family, and lets her in on the Sisterhood's tightest-held secret: It uses computer technology to keep track of the genetic database necessary for the organization's breeding program. (As established in the "Dune" movies, the ultimate goal of that breeding program was to produce a male Reverend Mother known as the Kwisatz Haderach — but for the purposes of this show, don't worry too much about that.)

The novel also features other characters including Manford Torondo, a leader in the anti-technology Butlerian movement, and Vorian Atreides, a war hero. From the royal family, there's Emperor Salvatore Corrino and his half-siblings Roderick and Anna. Valya's brother Griffin is also present, and there are mentions of her younger sister Tula, who features prominently in the show.

There's another important sister in the book as well: Doretea, who succeeds in becoming the second-ever Reverend Mother after Raquella. She and Valya are at odds, however, and Doretea puts the Sisterhood's mission in jeopardy by revealing the existence of its thinking machine to the Emperor. The sisterhood is forced to relocate and rebuild on the planet Wallach IX.

'Dune: Prophecy' isn't an exact adaptation of 'Sisterhood of Dune'

While the television series draws significantly from the history presented in "Sisterhood," it shifts some things around and includes characters that aren't present in the novel. Those characters include Desmond Hart, a soldier who comes into conflict with the Sisterhood, and royal half-siblings Ynez and Constantine Corrino.

Executive producer Jordan Goldberg told Business Insider that the series was "sort of" based on the novel, and that while the team adhered to the "Dune" canon in some ways, it also attempted to "infuse some new angles" into the story.

"There are bits and pieces of various different characters and plot ideas that we've taken [from the book] and fused in our 30 years later story with the Emily Watson version of Valya Harkonnen," Goldberg said. "That story is sort of our invention."

The good news is that there's plenty of "Dune" to go around, should HBO decide to continue the story. Brian and Anderson have written multiple novel series that tread "Dune" history both pre- and post-Paul Atreides, the hero from Frank Herbert's novels and Villeneuve's film adaptation.

"We would love to keep telling this story as long as they let us," Goldberg said of a potential second season. "There's so much to explore, so many angles to go. The characters that we've set up in the story, they have long legs."

"Dune: Prophecy" airs Sundays at 9 p.m. ET on HBO and is streaming on Max.