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

HBO

• "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."
• Here's what you need to know about the book, and how closely the show adheres to it.

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.