Three possible explanations come to mind to explain why Charles Stross's latest novel was given the title Neptune's Brood. The first, and most likely, is that the publisher wanted to emphasize that the novel is a sequel of sorts to Stross's Hugo-nominated 2008 novel Saturn's Children, and Neptune comes after Saturn on the list of planets whose names do not elicit snickering from an English-speaking audience. The second is that the last third of the story takes place beneath the waters of a distant planet, justifying both the reference to Neptune and the American cover's regrettable mermaid illustration. But a third reason to evoke water, one that probably did not figure in the calculations of the publisher or author, is that although the novel is set thousands of years from now in an era when the androids who survived humanity's extinction have spread to hundreds of star systems, it tells a story that, stripped to its essentials, could easily be set in the Caribbean of the late seventeenth century: Our brave protagonist Krina is looking for her sister Ana because they each have half of a map leading to a vast buried treasure. Desperate to leave port before anyone realizes what she's carrying, Krina enlists as a deckhand on a missionary ship which then is attacked by pirates.

All of these elements have been given a far-future space opera veneer, of course, and as one might expect from an author of Stross's imagination, this goes a lot farther than just transferring the action from islands and galleons to star systems and spaceships. Krina is Krina Alizond-118, a "metahuman" looking for Ana Graulle-90, her "sister" in that they are both copies of the same original individual, albeit with different behavioral tweaks. Instead of two halves of a treasure map, they carry the two encrypted halves of an incomplete Bitcoin-style peer-to-peer financial transfer. The Church in the story is not the Catholic Church but the Church of the Fragile, a powerful religious order dedicated to recreating biological humanity. And the self-proclaimed pirates turn out to really be insurance underwriters who dabble in skip tracing, led by a captain who with a straight face identifies himself as "Chief Business Analyst Rudi the Terrible" (p. 86).

Sometimes people are dismissive of genre stories that can be mapped to mundane templates this way, seeing them as lazy or inauthentic. That's not the case here, and the reason is that while the plot may be analogous to old-fashioned pirate stories, the setting hasn't been contorted to make that plot possible. This is hard science fiction, written at least in part for an audience that won't accept spaceships that act like sailing ships, and Stross clearly put a lot of time into working out the details of his world and making everything fit together harmoniously.

One of the most common stereotypes of hard science fiction is that the characters are flimsy cut-outs whose only real purpose is to act as runway models for technology, but with one big exception Neptune's Brood is innocent of this charge as well. No one has ever accused Stross of being the sort of author who puts characterization first and this novel won't change that, but beyond the first-person narrator Krina he has come up with a lively and eccentric supporting cast, and if none of them ever seem truly three-dimensional, none of them are around for long enough that this becomes a problem. Krina, alas, is as bland as they come, the sort of narrator whose characterization consists of a name, an occupation, and the vague sense that she is a good and well-intentioned person. Almost entirely passive, her role in the novel is to be captured by successive factions, allowing her to introduce us to them, to be taken to diverse locales, allowing her to describe them to us, and to be present while the plot happens, allowing her to explain it to us. As a character, she's in no way interesting, but as a conduit for the novel's ideas she's the figurehead for the real business of the novel: interstellar economics.

The most inventive idea here for seasoned genre readers will be the distinction between three different types of money: fast, medium, and slow. Fast money is what we would recognize as cash, issued by a planetary government. Medium money is a way to denominate assets that can't immediately be converted into cash, like real estate. It's not a new observation that as assets these aren't effective for interstellar trade. Cash or property from another star system isn't worth all that much without faster-than-light travel, since by the time you manage to get there, the cash might be inflated into worthless paper and the house might have burned down. What Stross adds to these two familiar asset types is slow money, a currency that's backed by the wealth of an entire star system and whose transactions must be signed by trusted third parties, which is to say, other star systems. That's where the "slow" part comes in: slow money transactions take years to complete because signals must cross interstellar distances before they can become valid. Like a normal currency, a star system's slow dollars can inflate or deflate in value, but the glacial transaction speed means someone owning slow money can trust that circumstances won't run out of control before they hear about it. Crucially, this allows slow money to be used to denominate debt held across star systems.

The novel begins with a quote from David Graeber's Debt: The First 5,000 Years, a non-fiction work that argues for finance in general and debt in particular as the driving force behind human history. Neptune's Brood posits a world even more centered around the concept of debt than our own. Krina was born owing a "debt of instantiation" to her mother, not a vague feeling of obligation but an enumerated debt codified in law and subject to interest, one that took her decades of hard work to pay back. Krina is fairly laid back about all this, resenting her mother but always qualifying descriptions of her childhood with comments like "I wouldn't want to mislead you into thinking we were harshly exploited" (p. 15). From within the system, Krina doesn't see much wrong with it, but as readers we see that by comparison to our own economy, the extension of debt into every sphere has made Krina's world a grim and heartless place where over time both power and wealth have gravitated almost entirely to those who control the financial system. This has some surprising implications when we turn to the particular sort of debt that most concerns the novel, the debt incurred colonizing new star systems.

For several decades now hard science fiction has struggled with the dispiriting energy requirements for space travel. Formerly the subgenre of techno-optimists who fervently believed in humanity's manifest destiny to conquer the stars, it has become increasingly difficult for its authors to figure out how to make the financial numbers add up just for colonizing the solar system, much less the brutal expanse of interstellar distances. In that context, Neptune's Brood paints a heartening future where an undaunted "humanity" spreads itself ever further in a wave of colonization that actually accelerates over time, but the reasoning is interesting and, to my knowledge, completely new. Colonizing another star system is such a stupendously expensive enterprise, we learn, that the only way the colony can hope to pay back its "debt of initiation" to its mother system is to launch colonies of its own and require payment of similar debts from them. Another contributing factor is the unchecked concentration of wealth, which has created a tiny elite who are wealthy beyond imagining. Their fortunes, one character asserts late in the book, "can only be realistically be depleted by the founding of a new solar system or two. And unless you choose to do that, it's going to hang over you for the rest of your life, dwarfing anything else you do" (p. 286).

This startling vision of reflexive greed driving humanity to an endless, exploitative expansion across the galaxy recalls a novel rather outside the hard science fiction tradition, C. S. Lewis's Out of the Silent Planet (1939). But where Lewis was willing to explicitly argue that one planet ought to be enough for humanity, Stross leaves us to draw our own conclusions. Neptune's Brood is dedicated to "everyone, everywhere who's ever looked at the stars and thought, 'I wonder if we could live there?'" and invites its readers to delight in futuristic swashbuckling, but the infrastructure that made all that possible has come hand in hand with gross inequality. Perhaps that was intentional, since many would say the same of our present world, but the next step after that conclusion isn't clear. The only sympathetically portrayed factions in Neptune's Brood either exist outside the slow money system or are actively trying to destroy it, but if that ever happened it seems likely that colonization and perhaps even interstellar travel would die with it. That Neptune's Brood asks good questions on this subject is laudable. That it has no real answers is a little less laudable, but very understandable; the narrative takes the easy way out, ending with a technological breakthrough that destroys the slow economy while still preserving the ability to travel between stars.

Those who find all this economic discussion interesting can rest assured that, for good or ill, there's plenty more in the novel. Many science fiction novels try to evoke the future by throwing unexplained words and situations at the reader. This approach can be wonderfully effective, but there's always the danger of veering too far from the world the reader knows and becoming incomprehensible, especially to those who aren't genre veterans already familiar with the tropes from other sources. Neptune's Brood takes the opposite approach, and instead of evoking the future, it explains it. Often at length.

Some of these infodumps, such as the long explanations of the tiered currency model, can be justified by the narrator's own preoccupations as a "scholar of the historiography of accountancy practices" (p. 16) or else the narrator's never-entirely-explained impulse to ensure her narrative will remain comprehensible to readers from a hypothetical successor civilization in the unlikely event her own collapses into a new dark age. But at other times, the text pauses to geek out about some science fictional novelty, like the physics of radiation eruptions from a young planet's mantle, for no better reason than that it's cool. Occasionally the narrator tries to preempt criticism with rhetorical maneuvers like "I am now going to bore you to death with the political economy of Shin-Tethys" (p. 127) but for the most part Neptune's Brood believes enough in the appeal of its info that it dumps it without reservation.

The novel is less courageous when it comes to the posthumanity of its characters. Estrangement of reader sympathy probably tops incomprehensibility as the most common failure mode of modern far-future narratives, but rather than apply the patient and thorough explanation it uses for the rest of the setting, Neptune's Brood goes long on the humanity and short on the post with its characters in ways that aren't really justified by the worldbuilding. Every character is what we would call an artificial intelligence, and though they call themselves human, the reality is that their bodies are mechanical constructs fully distinct from their minds, which can be copied, transmitted, and modified like the computer files they are. These fundamental differences mean that while the processes of life remain—they grow, eat, reproduce, and if not backed up properly they die—they are in most important respects different from humans. With humanity extinct for thousands of years, even if they were originally built as "metahumans" around human patterns, it seems reasonable to expect considerable divergence.

But other than the occasional use of non-anthropoid bodies (bodies which are still analogous to animals like squid which don't exist anywhere but Earth, assuming they even still exist there), nearly every character in the novel is recognizably human in the ways they think and act. They consume substances through their mouths instead of plugging in to the wall, they have a physical sexual drive even though the only time actual reproduction is mentioned it sounds like it involves copying a file and then opening it up in an editor, and almost all of them keep their mind strictly tied to a single physical body unless they need to travel interstellar distances, even to the point of getting information from the net by making their physical body look at a screen.

Any future can be nitpicked, but even if it doesn't make sense that, say, anyone in this culture would pay the energy cost to decelerate physical bodies from orbit and land them on a planet instead of just transmitting their minds to the surface, the overall setting is so imaginative and well-realized that to do so would feel unfair. The humanity of the characters, however, stands out as a problem. By itself it would be easy to accept as a sort of convention the same way that, when the narrator says she's explaining something obvious in case some reader in her future doesn't know about it, we accept it though of course we know that the explanation is really for readers in her past, namely us. But unfortunately the prose relentlessly signposts the inhumanity of its characters in a way that constantly brings to the foreground the disparity between their allegedly non-human nature and their very human behaviors. For example, after a traumatic experience, Krina tells us that "some obscure reflex threw my ocular lubricant ducts into repeated self-cleaning cycles, and I began to weep" (p. 101). This is just one of many examples of the text trying to have it both ways. Either Krina and everyone she knows is based so thoroughly on the human template that they cry, in which case she'd narrate this event as "I cried," or else they are artificial intelligences whose minds control bodies like we move video game characters, in which case this ought to read something like, "while my global stress variable incremented above a threshold that reordered my short-term priorities, my body sat frozen awaiting further instructions."

Lest we think this is some quirk of Krina's, other characters even do this in dialogue, such as this particularly egregious example from late in the story:

Before the dawn of history, when humanity was entirely Fragile and confined to a single planet, there was a species of wild organism that was highly prized as a feedstock by those protohumans. It was called a "truffle," and it was rare, and grew underground. Truffles were noted for their characteristic smell, but Fragile noses were not strong enough to detect them. So they took a different species of animal, a thing called a "pig." Pigs liked truffles and had a good sense of smell, so they were easily trained to hunt for truffles. But the truffles were valuable enough that, once found, the pigs were not allowed to eat them. (p. 296)

The character is using truffle-hunting pigs as an analogy, and it's a good analogy in the sense that it is very fitting, but it's not a good analogy in that it is wholly unbelievable that anyone thousands of years in the future would ever say this (indeed, the explanation is detailed enough to suggest an author apprehensive that even the present-day reader might not know about truffle hunting pigs).

There is a sort of sport in trying to couch the clichés and concerns of the present day in the language of the future, but it's the sport of a comic novel and feels out of place in an otherwise serious story. It's not that serious novels can't be funny at times, but that's best accomplished by characters saying funny things (as they do, for example, in otherwise unrelentingly grim novels if Iain M. Banks) rather than the author.

But while the tone may not be consistent, these wry moments fit together with the old-fashioned plot, the passive protagonist, and the detailed infodumps as part of a strategy to maximize the novel's accessibility to readers so they can grapple with the detailed economics at the core of the story without anything else confusing them. Stross even takes the nearly unprecedented step of having his narrator stop every seventy-five pages or so and summarize everything that's happened up to that point, just in case readers have literally lost the plot. Neptune's Brood doesn't totally neglect its plot and characters, but it plays them safe, trying to do enough so that they don't actively detract from the reading experience, but keeping them bland and inoffensive so that they don't distract from its real project. Those who read fiction principally for characters or plot won't consider this worth their time as there are countless books that do those things better, but for those who prioritize the speculation of speculative fiction, Neptune's Brood represents a genuine advance in science fiction's common understanding of the future.

Matt Hilliard (matt.d.hilliard@gmail.com) works as a software engineer near Washington, D.C. He writes about science fiction and fantasy on his personal blog Yet There Are Statues.