Vernor Vinge, a creditable writer if ever SF has had one, pronounces The Cassini Division "a brilliant novel of ideas" in an enthusiastic cover blurb. The trouble was, I found it difficult to detect one idea in the entire novel that was developed in detail or, more importantly, which may have provided the novel with a thematic focus. The Cassini Division is a novel that earnestly tries to address the ethical dilemmas presented by a future in which runaway technologies have divided the human race, in more ways than one. But in his efforts to present every side of an issue, MacLeod's results are glossy and superficial. It is a readable but ultimately unfulfilling novel that leaves you wondering precisely what the point was.
The story is set in the 24th century following a series of calamities, among them the Green Death, a genetically engineered plague, and the collapse of capitalism (MacLeod is an unabashed left-wing socialist). In the 21st century, a group of transhumanists called the Outwarders have developed the ability to upload themselves into computers, becoming the very first Greg Egan-style post-humans. The post-humans have moved out to Jupiter, claiming the planet and using legal excuses to justify their uploading the minds of human beings into robotic drones for slave labor. The post-humans are an all-around bad sort. They've been shooting nasty viruses, both electronic and physical, our way, which have obliterated all computer use on Earth (causing us to resort to the use of enormous "difference engine"-style analog computers). They've also demolished Ganymede and created a wormhole out to Sagittarius. But at one point the slaves managed to escape through the wormhole and resurrect themselves into physical bodies. The post-humans have since retreated into virtual reality, where a month of our time can be the passage of many years to them.
MacLeod's characterization of the post-humans as de facto evil isn't really supported. We're just supposed to take it as a given, which argues for a certain technophobia on MacLeod's part despite the fact that many of this novel's characters walk around in awesome nanotech outfits that can turn into anything, even a satellite dish. The protagonist of The Cassini Division is Ellen May Ngewthu, who works for the titular organization, the military arm of the Solar Union who have been doing their best to protect Earth from the post-humans' nanoviruses. When it becomes apparent that the post-humans are emerging from their virtual slumber, as it were, the decision is made to obliterate them once and for all with comets before they can pose any greater a threat to humanity than they already have. To this end Ellen recruits a physicist on Earth named Malley, on whose theories the wormhole was created and in fact after whom it is named. In an example of how MacLeod dashes through important plot elements in an effort to get to what I presume he considers the good parts, Malley, although he is a "non-co" who has rejected the Solar Union's socialist paradise, takes about two seconds to agree to accompany Ellen out to Jupiter.
Once there, at Malley's insistence, the Division actually establishes contact with the post-humans, who claim that all those viruses were a big accident and they really aren't such bad folks. To Ellen this is simply confirmation of their sinister, deceptive character. Malley also discovers how to navigate the wormhole and an expedition is made to New Mars, the planet on the other side that serves as the long-lost colony of Earth people once enslaved by the post-humans.
There's a lot of political and philosophical chit-chat going on in this novel, very little of which is substantial enough to grace with the label "debate." MacLeod's characters all have views on the moral problem of wiping out an entire species, and whether or not a super-sophisticated artificial life-form is really human. But none of these exchanges really does much to give the novel a firm thematic core. It's as if MacLeod is so determined to let his characters speak for themselves, without inserting any of his own biases into the discussion, that we're left with very little idea of whom to root for. Ellen is the book's "hero" only insofar as she is its protagonist. Yet she is strident and almost dogmatic in her views, which makes her often quite unappealing. A story about the possible genocide of an entire species ought to be perfect fodder for a character to undergo some profound soul-searching. Yet all we get are off-the-cuff conversations, some of them set at parties.
There are other problems. Often you can't tell whether or not MacLeod intends really to be taken seriously in this story. Dialogue exchanges many times are of the dreadfully cheesy sort found in bottom-drawer retro space opera. (Particularly when we reach New Mars, where the story reaches borderline absurdity.) Again, MacLeod, quite commendably, doesn't want to preach, but there are dramatically effective ways of conveying the ideas this novel wants to convey, and MacLeod seems indifferent to them.
As a hard SF novel, The Cassini Division also disappoints. Simply filling your novel with words featuring the prefix "nano-" doesn't qualify your book as a stimulating work of scientific extrapolation. Indeed, the scientific content of the book is close to nil until the final scenes.
Since MacLeod's other work has earned him a good deal of acclaim (including a Hugo nomination for The Sky Road), I suppose it will take my reading his other books before I can decide upon a fair assessment of his skills as a storyteller. Perhaps The Cassini Division is just a weak entry in an otherwise impressive résumé. Even the best writers have those.