If you're diving into the sand for the first time, I’d tell you to start where the ripple began: read Frank Herbert’s original six in publication order. That means beginning with 'Dune', then moving on to 'Dune Messiah', 'Children of Dune', 'God Emperor of Dune', 'Heretics of Dune', and finally 'Chapterhouse: Dune'. Reading them this way preserves the slow-burn revelations, the shift in tone and philosophy, and Frank Herbert’s evolving themes about politics, ecology, religion, and human nature. There’s a weirdly satisfying progression in how his ideas get stranger and deeper, and seeing that development the way readers did in the 60s–80s is part of the ride.
After you've lived through those six, decide if you want more scaffolding. The prequel and sequel books by Brian Herbert and Kevin J. Anderson—like the 'Prelude to Dune' trilogy ('House Atreides', '
house harkonnen', 'House Corrino') and the 'Legends of Dune' books ('Dune: The Butlerian Jihad', 'Dune: The Machine Crusade', 'Dune: The Battle of Corrin')—are convenient if you crave backstory on the Butlerian Jihad or the Atreides dynasty. They’re written in a different voice and feel more like modern blockbuster fantasy, so I usually recommend treating them as bonus material to read after the originals, unless you’re obsessed with worldbuilding and want the full historical sweep.
Personally, I read 'Dune' before watching the latest film and it made the movie hit harder—small details suddenly mattered. If you only have time for one book, pick 'Dune'. If you catch the bug, work through the original six and then branch out to the prequels, the sequels 'Hunters of Dune' and 'Sandworms of Dune' (which attempt to finish Frank Herbert’s arc), and the various companion texts like 'The Road to Dune'. It’s a long, sometimes weird, frequently brilliant journey—enjoy the spice and the silence between chapters.