The subtitle of Charles Stross's latest novel proclaims it to be ‘A Space Opera.’ I suspect a reader whose expectations are based on that label might be perplexed. Stross offers neither the cinematic action of classic space opera, the radical speculative physics of ‘new space opera,’ nor the hyperbolic curve of technology common to both forms.

In fact, so far as its scientific substance is concerned, Neptune's Brood is much closer to hard science fiction, usually regarded as the opposite pole of the sfnal universe from space opera. In the first place, its technology, though incredibly advanced, is also conservative, with radical innovations being centuries apart. Nearly all of it appears to be based on physics that we now understand, and on devices that we can at least imagine building, working in ways consistent with real science. This is, in fact, a setting where FTL drives appear primarily as a classic con game!

In the second place, a substantial part of the story turns on one of the great tropes of hard science fiction: rigorous world building, in the style of Hal Clement's prototypical novel Mission of Gravity. The world of Shin-Tethys is not ‘another Earth,’ but a planet of an exotic type not found in our solar system, which requires going back to the first principles of physics and chemistry to describe—a water world with oceans hundreds of kilometers deep. Stross gives vivid descriptions of the exotic hazards of his undersea setting. This is the kind of world-building that Poul Anderson made a specialty of, with the benefit of the newest developments in planetary science.

So far as plot is concerned, though, Neptune's Brood belongs to quite a different genre, which might be called "science fiction noir." It has most of the classic elements of film noir, including a plot centered on the investigation of a mystery; elaborate conspiracies behind the scenes; and the corruption of wealth and power. It even has a classic maguffin, the Atlantis Carnet, which looks like a pointed reference to the Maltese Falcon.

Stross has written other science fiction mysteries—notably Halting State and Rule 34—but their sfnal aspect was near-future science fiction, with hints of cyberpunk. Neptune's Brood is a mystery that turns on the physics of slower-than-light interstellar communication and commerce. This is economic hard science fiction, where the economics is as ‘hard’ as the physics and planetology. Stross writes knowledgeably about insurance, banking, and accounting—and about fraud and rent-seeking, the criminal side of market activity. The novel's central ‘marvelous invention’ is the interlocking system of fast, medium, and slow money, designed to meet the needs of an economy spread across many light-years, with transactions that can take decades to complete, and investments such as interstellar colonization that don't pay off for centuries.

It should be noted that Stross's view of economics is not "libertarian” in the sense familiar to most LFS members. One key passage in the novel asserts that any society where payment of debts is enforced inevitably has an authoritarian and repressive government; another asserts that debt as such is slavery. By this definition, a free society would have to be one with no debt, no borrowing, and no capital markets—which seems to equate to a socialist society of some type. A key sequence in the novel has the protagonist encountering an ethically superior society that in fact is internally communist though, to Stross's credit, he defines this not in terms of ‘post-scarcity,’ but as the result of a much higher bandwidth of interpersonal communication, which at least is addressing the problem of economic calculation rather than imagining it away. And more generally, however debatable Stross's view of economic relations is, it's also informed by a lot of actual knowledge of market transactions and financial institutions.

Neptune's Brood is set in the same universe as Saturn's Children, but isn't exactly a ‘sequel’ to it. For one thing, it doesn't share the earlier novel's wholesale borrowing of late Heinlein tropes. The main continuity lies in the characters of both novels being almost entirely ‘robots’—though Stross has come up with a much more sophisticated vision of robotic existence; his characters are humanoid beings formed from ‘mechanocytes’ that function much like natural living cells, but can withstand much more challenging physical environments. Stross envisions robots spreading out into the solar system and then to other stars, while human beings, ‘the Fragile,’ die out, being remembered mainly by a robotic religion. But though this is the underpinning of Neptune's Brood, it's not what it's about. The real subject of Neptune's Brood is debt and the conflicts to which debt gives rise. And if that doesn't seem like a subject for space opera, it makes a plausible one for a mystery novel.