First, let's get the obvious out of the way; Dune: The Machine Crusade is another prequel to Dune and a sequel to The Butlerian Jihad. It has all the drawbacks and bonuses of a sequel; if you haven't read the first in this series of prequels devised by Frank Herbert's son Brian and Kevin J. Anderson, you may feel a little lost at first. The good news is that Herbert and Anderson manage to fill in the blanks early on with a nicely written recap in the prologue (much as the Frank Herbert did with each sequel to his classic Dune novel).
I imagine that Herbert does much of the plotting based on Frank's original background notes and that Anderson does more of the hands on writing. At least it seems that way. In terms of style The Machine Crusades reminds me more of Anderson's novels than Brian Herbert's novels. But both had complimentary, similar styles so it's possible they rewrite each other.
Either way, the plot continues. With the destruction of the Omnius on one of the settled worlds, humanity managed to strike a blow against the computer that created hope. The Cymeks led by Agamemnon struggle to regain their lost power against Omnius all the while fighting humanity as well. Time doesn't matter to Omnius or the Cymeks but it does to Serena Butler. Nearly a quarter century has passed since the computer's henchrobot murdered her son as part of an "experiment" to discover humanity's emotional movitation to fight even when they are clearly defeated. She and the others struggle on in battle against Omnius.
Agamemnon's son Vorian Atriedes and Xavier Harkonnen continue their uneasy alliance in fighting Omnius. We also get our first glimpse of humanity's discover of "folding" space and the impact it will have. On Arrakis the Fremen come into their own as fierce fighters led by Selim Wormrider. We begin to understand how this distant, remote and poor dust speck in the cosmos comes to occupy center stage in Frank Herbert's original novel.
This sprawling epic sets the stage for what's to come later in Herbert's original trilogy. Although it's uneven and the plotting is a bit more awkward here than in the some of the previous novels in this series, The Machine Crusade accomplishes most of its goal. It also sets up another potential sequel. To give Brian Herbert and Kevin Anderson credit, the series they've created does credit to the original novel and Frank Herbert's memory. There are a number of interesting philosphical questions examined here. To the author's credit, they don't let the philosphical questions bog down the action. Both attributes contributes to the strengths and the flaws of the novel; the questions linger on too long and the battles are drawn out a bit too much. At times it seems as if the authors are struggling with the epic tale they are trying to tell; it's as if they are trying to come to grips with the size of the story they need to tell and control it. Even when it veers out of control, The Machine Crusade is still better than most of what passes for science fiction today.
Nevertheless, like its immediate predecessor, The Machine Crusade has an epic, vast scale that the story and characters deserve. It's clear that Brian Herbert in continuing on his father's story chose to do so in a fashion that wouldn't just cash in on (and hence dilute)the original novels. Instead, he and co-author Anderson have tried to come up with a series of space operas as rich in character and scope as the original series. While the dialog can be frequently clunky and the characterizations a bit too sketchy for some, these are minor flaws on this large canvas. They boldly move forward using all the colors of language that they can to describe this epic tale. If words occasionally fail them, it's because the story, like much of Herbert's original epic, can be overwhelming in its vast embrace of science, religion and politics.
If Brian Herbert and Anderson can continue to create novels this complex, the Dune series has a future as more than a cookie cutter space opera series. If they occasionally borrow from some of the sf films that have come out since Frank wrote the original novel, it's only fair; George Lucas and many other film directors borrowed liberally for Frank's imagination, integrating into their own projects and calling it their own.