Neptune's Brood is Charlie Stross's newest, weirdest and most thought-provoking book. It's technically something of a followup to Saturn's Children, a funny, sexy late-Heinlein robosexual pastiche, but as the action takes place millennia after Saturn, and as the mood and substance of this book are totally different from it, they're hardly related, properly speaking.
What Neptune's Brood is closely related to is a 2012 economic history book called Debt: The First 5,000 Years, an absolutely indispensable — and enormous — treatise on the history of money and its relationship to inequality in society. Debt, written by an anarchist anthropologist called David Graeber, has been something of a cause celebre in science fiction circles, mounting a serious challenge to the consensus about the long sweep of history (and thus the future). But Stross's book is the first novel I've read that tries to apply all of Debt's lessons (I have bits of them in my novel Homeland and its followup novella "Lawful Interception" — but in a much more minor way) and it goes a long way to accomplishing it. This is something of a marvel.
Neptune's Brood concerns itself with the clonal descendants of an immortal, fantastically wealthy transhuman called Sondra Alizond-1. Alizond's lineage is rife with bankers, forensic accountants, historians of money, and other arcane types of financier, and they are each born with an instantiation debt to their mother, which they have to work off by laboring in the finance mines of New California, a starfaring civilization that Sondra Alizond-1 secretly rules.
The story revolves around Krina Alizond-114, a historian of a specific kind of advance-fee frauds, a scam called the FTL Fraud — a kind of Ponzi scheme based on rumors of a faster-than-light drive that will destroy interplanetary economics. Krina is a mendicant financial-research nun on a study-pilgrimage to a distant world where one of her clonal sisters awaits her, but when the sister goes missing, she finds herself hot on the trail of an enormous conspiracy that unravels to reveal the truth about the greatest financial fraud in galactic history.
The unraveling of this fraud, and the economic system that Stross establishes through it — part bitcoin, part bankster syndicate, part lightspeed-lagged mercantalist empire — is one of the most fascinating ideas you'll encounter in the pages of a science fiction novel. That it is liberally garlanded with Strossian touches — pirate underwriters, zero-gee vat zombies, socialist squid — is icing on the cake. And though this is a novel of big ideas, comical speculation, and high weirdness, it is also a window onto the cruelty of bank-fraud and corruption in the monetary system, the coercion at the center of our financial consensus.
This is a wonderful book, but it is by no means Stross's most readable. The ideas are so plentiful and the story revolves around such a baroque future that sometimes the story itself gets lost amid the argument. But that's ultimately a small price to pay for such a wonderful bouquet of ideas.