Final segment in the Dune Chronicles but rumor has it that Frank Herbert left a lot of his notes on a 7th book behind.
What an Amazon.com customer says:
Comparatively speaking, I would rank this book very close to the first Dune novel in the series. It has a huge (and I do mean HUGE) build up from the beginning of the novel until about fifty pages from the end when Herbert dumps the proverbial soup into our laps. But there are many questions left unanswered at the end (not that all questions SHOULD be answered but I felt that a sequel was sure to come had Frank Herbert not passed away before he could finish the series). I've heard that Brian Herbert, Frank's son, discovered a seventh Dune manuscript in a safety deposit box after his father died. If this is true, I can't wait to see it in print. If it's not true, then we may never know what the 'master' had in mind.
But enough of that...onto the book itself!
The story is that of the Bene Geserit sisterhood and their war against the wicked 'Honored Matres' who've returned from the scattering and has threatened to wipe out all of the BG sisterhood. Meanwhile, the BG's are turning Chapterhouse --- their last sisterhood stronghold planet --- into a desert planet and bringing back the worms of Dune to this planet in hopes of starting a new cycle of sandtrout/worm/spice/sandtrout, again. Strong in this story is that of Duncan Idaho and Murbella, the captured Honored Matre from the fifth Dune book. They are [multiplying] like rabbits still in their no-ship prison and the BG sisterhood takes away the babies hoping to find genetic markers that they haven't seen before (continuing on in their quest for a perfect human). Also at the forefront is that of Odrade, the Mother Superior of the BG, who sees where their paths with the Honored Matres must lead. It is a giant melting pot that began with Leto II's rule (the God Emperor or the Tyrant if you prefer). The BG and the Honored Matres must become one sisterhood for them both to survive. Odrade sees this and passes her sisterhoods internal lifetimes on to Murbella after completing her training and watching her go through the spice agony.
In the end, the melting pot is achieved thanks to Odrade's manipulations and Murbella's Honored Matre's training. But there's a lot left out to indicate that more would have been forthcoming had Herbert not died. Duncan, Sheeana, Scytale, the Rabbi, and a wild-reverend mother, escape in the no-ship and head off into the unknown; even they don't know exactly where they end up. And, it appears, the gods don't know why this was done or where they will end up.
Questions: Who was chasing the Honored Matre's? Who were the handlers of the Futars and where did Futars originate from? Will Chapterhouse become another Dune world? Did Duncan and his runaway band in the no-ship take a worm? If so, what will they do with it? What will happen to the Guild now that Chapterhouse is turning into a Dune world?
Many questions...will there be answers. We'll just have to wait and see, I guess.
My summary: Dune goes out in style.