A group of government agents are sent to investigate a mysterious farm in Oregon. The farm is a front for a massive cult attempting to build a society modeled on an insect hive, oh and they are also building a super weapon capable of destroying the world.
As a reader you naturally want to support the humans against the bug people, but Herbert goes out of his way to portray the agents in completely negative terms. The agents never experience a positive emotion, they are all driven by anger, fear, jealousy, and hatred, and they betray and undermine each other at every opportunity. The hive people by contrast are cooperative and supportive but their culture is repellent on almost every level. They place no value on individual life and the bulk of their population is chemically neutered, pacified, and have their language skills removed to be more like worker insects. You would expect a hive to be a matriarchy with a queen, but the elite of the hive are all male and the females are portrayed as sex obsessed and not too bright. Finally, they convert some of their prisoners into "sexual stumps," a term I will not explain but suffice to say it may be the most grotesque image I have come across in fiction.
Herbert often mixed horror with his science fiction and I kind of wished he had focused more on the horror in this novel. A lot of time is wasted with the boring incompetent agents who manage to get themselves captured and killed with clockwork regularity. The grotesqueries of the hive are where the book gets truly interesting. Herbert was a master of world building, as he demonstrated in his massive Dune series, and I wish he had spent more time exploring the bizarre and nightmarish world of the hive rather than all the government agent business.