This is the second novel in the Dune: Prequels series. It's basically setting up the major plot points that are going to occur in Dune. Even though it's titled House Harkonnen, the events in the story tend to oscillate between House Harkonnen and House Atreides with some sections devoted to Emperor Shaddam IV (House Corrino). The Tleilaxians that have conquered Ix are getting under everyone's skin. Their lead researcher is on the cusp of a major breakthrough with synthetic "spice," which threatens the established economic base of the Known Universe, as well as the power structures keeping that economy in place.

Duke Leto Atreides has had enough of Harkonnen treachery and the Emperor's tepid support. He launches a devastating attack on a major Harkonnen stronghold. He also pledges his full support to his childhood friend, the exiled Earl Rhombur Vernius of Ix. Together, they begin a daring campaign to recapture Ix from the vile Tleilaxians, who have enslaved the native population for their obscene biological experiments. We also witness the birth of Paul Atreides, who is destined to reshape the Known Universe.

Over ten thousand years before the present era in the Dune universe, machines, led by the nearly omniscient and omnipotent Omnius, are conquering the Known Universe one planet at a time. "Cymeks" -- disembodied brains in robot bodies -- serve as generals in the robot armies, as they still possess the creative spark of innovation that machines are lacking. The humans wage guerrilla warfare against the machines, hoping to one day free themselves from their robotic masters. The Butlerian Jihad is THE key historical event in the Dune universe--their calendar starts from when humans are freed at the conclusion of the Butlerian Jihad, named for Serena Butler, one of their leaders.

One of the problems with prequel novels like this is that it does rely a lot on "memberberries" to tell the story:

• 'Member the "spice" that's central to the original Dune? Well here's the story of how it became the Known Universe's hottest commodity!


• 'Member the rivaly between House Atreides and House Harkonnen? Here's how it all started...


• 'Member the Holtzman generators that can fold space/time, suspend gravity, and provide personal shielding? Meet the man who created it, along with his talented assistant who made the real innovations!


• ...and so on.