House Harkonnen is the 8th novel in the Dune series when read chronologically and the second in the third overall prequel trilogy (aka, the Prelude to Dune series) to the original novels written by Frank Herbert. The book was published in 2000 and was again written by the combination of Kevin J. Anderson and Frank Herbert's son, Brian. Like the first book in this trilogy was not entirely focused on the Atreides, this book is not focused solely on the Harkonnens. The story jumps between Caladan, Corrino, Arrakis, Geidi Prime, Ix, Wallach IX, and Lankiveil and tracks Leto, Vladimir and Abulurd Harkonen, Emperor Shaddam Corrino, Duncan Idaho, The Fremen (with the focus on Liet Kynes), and the Benne Gesserit. To the extent that the book is focused on the Harkonnens, it mainly deals with Baron Harkonnen's maneuverings against all of the other major players.
The hardcover version of the book is just over 600 pages, and as I said above, the book jumps from one storyline to the other. Most of the storylines are separate, but some elements intersect with each other here and there. The events of the novel are set a few years down the line from the end of the novel House Atreides and it has a couple of short time jumps throughout. Most of the book is relatively slow-paced, but the story picks up a lot in the last handful of chapters (which was enough for me to bump it up to five stars). The big points in the book are the development of Leto and Jessica's relationship, Baron Harkonen's plots to take down House Atreides, Emperor Corrino, and the Bene Gesserit, Emperor Corrino's attempt to produce spice independent of Akkaris, the Bene Gesserit's plans to create god-like bloodlines, and Duncan Idaho's swordmaster training. Ultimately, the book is setting up the original Dune novel and laying out the backstory for the two original trilogies based on Frank Herbert's notes and unfinished works. It makes what was already a sprawling story even larger. It is not an easy book to read because of the fact that it has a lot of characters and jumps between storylines. But, if you are a fan of the sci-fi genre, this (and the other prequel novels) are worth your time to read. I am reading the novels in chronological order so I have not yet read the two original trilogies written by Frank Herbert, and I am not sure how this compares to those books, but this is written in pretty much the same style and tone as the other prequel novels, so if you like those, you will probably like this one.