Reynolds is best known as a "hard science fiction" author. This is likely as much because of his real-scientist background as because of his work. He himself has been struggling against the label. "Some of the science in my book is real, and some of it is made up," he says in the acknowledgements to "Pushing Ice."
As with many of his books, the science in "Pushing Ice" starts with things that we can concieve based on the science we know now. The Rockhopper finds comets and pushes them back to earth for mining. When the comets can't be used for some reason, it blows them up so no one else can use them. As with many of the books, as time goes along, alien technologies start to arise that are barely imaginable based on the science we understand today.
This may be surprising coming from a "real scientist," but not so much given that Reynolds is an astrophysicist. Most of us in our daily lives deal with a small little domain around us that only involves things we care about, and are only vaguely aware that we are a tiny little scum of organic matter on a single planet on the end of the arm of a galaxy that is one out of a billion or so. But an astrophysicist has his nose rubbed in humanity's insignificance in the universe every day. This song is an astrophysicist's day to day experience. Consequently it's not so surprising that Reynolds would frequently have humans encountering tech that makes anything we've ever imagined look like a joke.
There are three significant alien species in "Pushing Ice." The first is the Spicans, who make the trap-like fake moon that drags the Rockhopper and its crew hundreds or thousands or millions of light-years away, as well as into the future. Ths Spicans never actually appear; only their technology does. The second is the Fountainheads. The Fountainheads are more experienced, more technologically advanced, and wiser than humans. They hold knowledge back from the humans based on the belief (probably correct) that if humans have certain kinds of knowledge or technology they will destroy themselves with it.
Then there are the Musk Dogs. The Musk Dogs are another inhabitant in the sort of "sentients' zoo" into which the humans of the Rockhopper find themselves confined by the Spicans' trap. The Fountainheads warn the humans early on about the danger of listening to the Musk Dogs. "They will offer you the world, and if you take it you will lose all," says McKinley, the human contact of the Fountainheads, who warns there is no safe level of exposure to the Musk Dogs. Needless to say, somebody takes what the Musk Dogs have to offer.
The central plot of the book is the struggle for power between the former friends, later vicious enemies Bella (the captain) and Svetlana (director of flight operations). Both characters are sympathetic, and both dominate different parts of the narrative. Each has her flaws, and each makes terrible mistakes. Bella's flaw is an excess of caution, and a reluctance to act when it's necessary. Her major mistake is not turning the ship around early on when Svetalana discovers a shortage of fuel to investigate the Spican object, formerly Saturn's moon Janus.
Svetlana's flaws are pride and rashness. Her big mistake is cooperating with the Musk Dogs, who claim they just want to tap the power sources for Janus, but really have much more evil intentions.
The Musk Dogs are beautiful inventions, but stretch the story far beyond the traditional hard-scifi boundaries. The Musk Dogs fly a ship that looks like, and in most ways is like, a gristly drumstick. Their pysical appearance is hideous.
The alien looked like two or three dogs fighting over a scrap of meat; an unruly mass of mismatched limbs, fur the color of sun-baked mud;too many tightly-packed eyes over a toothsome black muzzle. It was difficult to make out its basic body shape, for the creature kept scratching and scrabbling and pissing, arcs of streaming urine spraying from too many places...
They are completely fractuous within their ship; early on a Musk Dog tells Svetlana it will only continue to work with her if she betrays a different Musk Dog, leading to its death. They mark their possessions, (including Svetlana), by marking on them with a noxious musk-like substance.
But leading up to this encounter, we have watched the small crew of the Rockhopper divide and squabble, kill each other, switch allegiances, lie to each other, and carry grudges like they inherited them. Introducing the Musk Dogs, the Fountainheads warn that it will be difficult to resist them, warning "they're factional animals as well."
The point is clear. We're a lot more like the Musk Dogs than the Fountainheads. In this way, Reynolds resembles Jonathan Swift of Gulliver's Travels more than Isaac Asimov. Reynolds introduces aliens that expose us, reveal our weaknesses and strengths.
And yet he takes it a bit deeper than that. Because human squabbling, while it appears a weakness at first, slowly reveals itself to be its own kind of strength. The two greatest mistakes of the story, one by Bella and one by Svetlana, turn into greatuer successes for humanity. Bella's misguided decision to stay with Janus turns into a success when Svetlana realizes her attempts to escape it are useless, and devotes her attention to landing on it. But if it hadn't been for Svetlana's attempts to escape it they'd never have known what was going on. And Svetlana's mistaken decision to cooperate with the deceptive and cruel Musk-Dogs results in a passkey to escape their part of the sentients' zoo before the Musk Dogs blow it to smithereens.
In other words, in both cases two longs make a right. Reynolds seems to be implying that instead of overcoming our human fractuousness, we must embrace it. Our struggles between two extreme points of view will average out to a point of view better than each.
I have heard that in our own minds different ideas "compete" to see which is stornger. Does this mean our squabbling is like neurons firing, and we as a society are a brain? I doubt it. But maybe with work we will get there.