This book contains five short stories, supposedly left out from other novels. They're entertaining, and, like the other pre-Dune books by Brian Herbert and Keven J. Anderson, they will give you a clearer understanding of Frank Herbert's original DUNE novels.
As for Frank Herbert, I've read all six of the DUNE books, but I prefer to go up to Children of Dune, and if not that, God Emperor of Dune. As for the last two novels I could not get into them.
That said, of the five stories, two of them do relate to the last two last two novels, and reading them, I did get a clearer understanding.
"Treasure in the Sand," the third story (I'm not covering them in order), takes place right after "Heretics of Dune," after its destruction, where an expedition comes the the destroyed planet Rakis (Arrakis) to search for any artifacts to take back for preservation of history, but find things that would never expect. I liked this story because in "Heretics" when Dune is destroyed, the description is only one or two sentences long, and if you are not careful, you'll miss it. There is no long, drawn out description that will set the reader on edge.
In "Sea Child" (during "Chapterhouse Dune) a sister from the Bene Gesserit is exiled to an island on an ocean world, held prisoner by the Honored Matres, the nemesis of the Bene Gesserit, both being sworn enemies. One sister, named Corysta, befriends a creature, a human genetically engineered to live in the sea.
If you liked these two stories, you might be able to understand Herbert's last two books a lot better. They are different from the other four books and you may or may not like them.
The first story is about Paul during his pre-Dune days, under Jessica's wing, who's father is about to be married (not to Jessica) for the sake on convenience of the family. Marriage for love is rare in this environment. Paul decides to venture to a jungle, to obtain silk from giant silkworms. Enough said.
The last two stories, "Dune: Blood and Water" and "Fremen Justice" are stand alone stories from Dune: House Harkonnen. "Blood and Water," I recall is in the mentioned book, but probably in another form. Abulurd Harkonnen, living on Lankiveil, and is a fur whale merchant, the "white sheep" of the Harkonnen family. His son, Rabban, returns home to visit, but, to his father's amazement, turns out to be evil and messes up his father's family business.
"Fremen Justice" is where a shipload of young recruits patrol an area of Arrakis, capture a small sand worm, drown it in water for it's bile, and poisons a cistern nearby, as a practical joke. The town's people die a horrible death, but some Fremen witness the entire scene and take action to impose justice on those responsible.
That's just about it in a nutshell. You can only get this on Kindle, but it's worth the money to buy it. It isn't much, it's a short book, and can be read in two or three sittings, which is good if you have nothing else to do.
If you are a Dune fan, get the book. It will entertain you for a few hours, at least.