One of the problems with writing novels for the trade publishing business is that you're not just writing for your readers; you have to keep one eye on the internal structure of your publisher's business. Prior to the 1980s, trade publishing ran on much the same lines it had in the 1880s; small family-owned or run businesses where editors acquired and edited books, then sent them down to the production department to be typeset and then printed and bound and warehoused. But a wave of corporate take-overs up-ended the entire game board in the 1970s and 1980s, and these days the internal logic of publishing bears little resemblance to the business in days of yore. Any part of the pipeline that can be outsourced has been outsourced for decades: and while editors still edit, their job is now tightly integrated with marketing, and they can't (usually) buy books that they can't convince the marketing department are commercial propositions.
So when you've written a successful novel, the first thing any editor says to you is, "that was great! Can you write me another book just like the last one, only different?" By which they mean something that is easy to explain to the marketing folks without requiring them to read the entire manuscript (because marketing are responsible for selling maybe 2-3 new titles a week, and they just don't have time).
Back in 2007 I wrote "Saturn's Children", thinking that it was a one-shot: a late-period Heinlein tribute novel. And indeed, there was no way I intended to go back and write about Freya ever again. (She's one of the most annoying protagonists I ever came up with. Alternately chatty and whining, a vacuous underachiever, traumatic origins or not: it was a pleasure to push her out of my head when I finished that book.) But some folks seemed to like it, and when Jonathan Strahan came along and asked me to write a story for his new hard-SF anthology, Engineering Infinity I came up with an idea that only made sense in the context of Freya's universe and it's rather primitive starships. Hence Bit Rot.
Having written "Bit Rot" it seemed to me that there was some scope for exploring what happened to the Freyaverse some thousands of years after the events of "Saturn's Children". But there things rested until 2010.
Now, in 2010 I signed a new three-book contract with Ace and Orbit (Ace for North American rights, Orbit for UK/Commonwealth rights). The original contract was for a Laundry Files novel (The Apocalypse Codex), an unspecified space opera (as light relief between Big Jobs), and a third near-future Scottish SF police procedural to follow "Rule 34" and "Halting State". That novel, "The Lambda Functionary", failed to take off: firstly because I got too ambitious, and then because I ran into the Scottish political singularity. (It may yet get written, in drastically different form, after the fallout from this month's referendum settles. But it can't be published for at least three years due to other books that are already locked into the production pipeline.) Instead, I hastily wrote a quick Laundry Files knock-off that turned out slightly better than expected: The Rhesus Chart.
What about the book in the middle?
The book in the middle was meant to be a light-hearted space operatic caper. I'd established a much-slower-than-light universe in "Saturn's Children", and posthumans who could survive the harsh environments and protracted time scales implied by it. How about sending a protagonist on a tour of known space?
Well, at the first step, my suspension of disbelief broke. Because space travel is so hard in the Freyaverse that nobody in their right mind would do it, unless the stakes were unbelievably high—and they had a very low estimate of their own self-worth. In fact, come to think of it, space colonization was itself a ludicrous idea; how on earth could it pay for itself?
Nevertheless, I persisted. I realized that I needed an economic framework, otherwise the whole idea collapsed at the first hurdle, leaving me with only religious fanaticism as a plausible motive for space colonization. And while religious fanaticism features in "Neptune's Brood" (the Church of the Fragile are what you get after 5000 years of uncritical acceptance of the nonsensical "we can't keep all our eggs in one basket"/"what if life on Earth is wiped out?" arguments advanced by would-be space colonists today: our robot offspring are going to ensure that humanity spreads to the stars, kicking and screaming and dying in large numbers), religious fanatics aren't terribly engaging characters in a work of fiction.
And that's when the idea of different speeds of money hit me.
In the late-period Freyaverse, money comes in three kinds: fast, medium, and slow. We are all used to fast money; it's what we use today. It's a medium of exchange of value and it correlates with economic velocity: the hotter/faster an economy is moving, the more money circulates. You can't meaningfully transfer fast money between star systems (or even sub-systems in orbit around a common star, such as the separate moon systems of different distant gas giants) because the economies are not directly coupled: no physical goods are actually worth shipping across such distances. (I'm putting a lower threshold on the cost of a single starship mission in the Freyaverse of roughly one year of GDP for an entire solar system; in today's terms, if we had the tech to build one, that would be around $50Tn, or 5-6 times the annual GDP of the United States.)
In addition to fast money, there are long term instruments that act as reservoirs of value. Real estate is not terribly liquid—you can't take a thousandth of your house to the supermarket and use it to buy provisions—but it's still recognizably valuable. And it persists; real estate investments may hold value for decades or centuries. And because they're interchangeable with fast money, at what is effectively a wildly skewed exchange rate, these properties can act as buffers against fluctuations in the fast money economy.
The Freyaverse recognizes this by denominating investments of this type (not just houses but pyramids and space elevators and planetary terraforming projects) in a currency of their own: medium money.
But starships in the Freyaverse are slow—typically cruising at 1% of lightspeed. At this speed, Alpha Centauri is nearly 500 years away; stars with known planetary systems may take millennia to reach. Communication is a lot faster: colonized star systems use modulated laser transmissions to beam data back and forth, including the uploaded, serialized minds of people who want to travel. But what kind of currency (even for a species as long-lived as our posthuman mechanocyte-based successors) can possibly be used to intermediate exchanges of value across interstellar distances? Or to settle debts amounting to the cost of building a new colony, when that kind of sum is equal to entire years of economic productivity?
Slow money is a digital currency backed by debt—the debt incurred by constructing a new interstellar colony. To exchange slow money tokens requires something like (but not identical to) David Chaum's Digicash; all transactions need to by cryptographically signed by a trusted third party. With slow money, rather than relying on a "banker", each party can operate as a banker—but bank A can't sent cash to bank B without getting the transaction irrevocably notarized by bank C. By putting the third party in another star system, both participants in the exchange can verify that they're not being scammed, because to get your digicash packet countersigned by your banker you need to literally aim your laser communicator at their home star system. And wait. And wait a bit longer, because this whole process takes ages—slow money (thanks to requiring notarization/acknowledgement) travels no faster than a third the speed of light.
So, setup: I generated a character (subtype: girl with a mission; sub-subtype: as utterly unlike Freya as I could make her, which is why she's a middle-aged accountant), put her in jeopardy (trying to get from a highly dubious space colony to a water world, she signs on board a damaged vessel crewed by religious fanatics for a working passage), and sent her off to have adventures.
Then, midway through the first draft, this book fell on me.
The book in question was Debt: The First 5000 Years by David Graeber, and it was to 2011 pretty much what Piketty on Capital is to 2014. Short version: Graeber is an anthropologist, not an economist. His thesis is that to the extent that economics is the study of how we allocate resources, this is essentially within the domain of anthropology: and some of the central narratives of economics are inconsistent with our understanding of how human societies operate. (If you read no other part of the book, look for his demolition of Adam Smith's account of the emergence of barter among primitive peoples. Barter, Graeber points out, isn't something that emerges, and that acts as a precursor to the development of money: rather, barter is what we get in atomized societies when fiscal systems collapse and nobody trusts their neighbours. True primitive tribal societies run on interpersonal debt and/or honour systems: everybody knows what their neighbours owe them, so there's no need to provide an immediate exchange for items of value received.)
But anyway: "Debt" gave me a critical tool to look at the economics of interstellar colonization in the Freyaverse. And a tool for thinking about why colonies might be founded. Colonization is expensive, so to create a colony mission incurs a huge amount of debt, denominated in slow money (because this is the only currency that can survive the gulfs of time and space involed). The easiest way to obtain the slow money with which to pay off your star system's debt of instantiation (and interest) is to grow rapidly and send out your own colonies, in turn, which allows you to issue cash instruments redeemable against their debt, much as banks today use lending as collateral for generating new money.
Voila! Just add banking fraud, murderous matriarchs, alien space bats, talking squids in space, a water-world and the worldbuilding thereof (see also part 2), and you have a parable for our times about the banking crisis and the spiralling growth of debt that is rapidly enslaving us to a floating pool of transnational financial instruments that nobody really understands or owns.
"Neptune's Brood" was simple, really: just a light-hearted space opera that accidentally turned into an exegesis on how to design an economic system to answer one of my earlier core criticisms of the proponents of space colonisation: who's going to pay for it?.
Two final notes.
Firstly, the ending isn't up to snuff. I'm sorry. I tried to do it justice, but I ran out of time. I had twelve months of wall-clock time to write the book, but throwing half of the first half out and re-doing from scratch after bouncing off "Debt" cost me a couple of months, and then I realized that I just didn't have time to spend an extra year or two polishing it. So I gave it the best ending I could, but to this day I have the nagging feeling that somewhere out there in memespace the real ending to "Neptune's Brood" is floating around, waiting for me to have the time to haul it back in for a Director's Cut re-release with extra found footage.
Secondly, "Neptune's Brood" was shortlisted for the Hugo award in 2014 ... and lost, by a wide margin to Ancillary Justice by Ann Leckie, which made an extraordinary clean sweep of the SF field awards in a manner that probably hasn't happened since William Gibson's "Neuromancer" swept the boards in 1985. Ah well: congratulations to Ann, who seems to have somehow single-handedly relegitimized space opera (it needs that to happen every decade or it stops being "new", or something like that)!
... And a third and final thought: this universe isn't dead. I drove it into a lamppost with that ending, the bumper's crumpled, the radiator's leaking and the transmission is making an ominous whining noise, but I'm pretty sure I'm going to take it out for another spin one of these years, unlike the Eschaton universe. Unfortunately it may be a long while; I seem to be writing only near future SF and urban fantasy these days ...