FOUNDED IN 1997, helmed by Jason Williams (publisher) and Jeremy Lassen (editor-in-chief), Night Shade Books has in the last few years made a concerted and largely successful effort to establish itself as one of SF and fantasy’s talent-spotters. They have published a slew of well-received first novels, by writers such as Will McIntosh, Rob Ziegler, and Kameron Hurley, that have been notable for combining conceptual ambition, political engagement, and narrative vigor, and for not being overly strict about genre borders. Sometimes these qualities may be pursued at the expense of sensitivity — witness the critiques of Paolo Bacigalupi’s The Windup Girl, almost certainly Night Shade’s best-known title, for its construction of racial and gender tropes — and a year-long suspension from being a qualifying market for membership of the Science Fiction and Fantasy Writers of America suggests that the company may at times have been a better friend to readers than to authors; but the impact of Night Shade’s list on the field deserves to be recognized.

And so here is E.J. Swift’s debut novel, Osiris. Four hundred years downstream, we’re in a future that is, if not a consensus of the field, pretty common: ecocatastrophe has wrecked the planet, to the point that, at least so far as its inhabitants are concerned, there’s no point venturing beyond the titular city-state. This is humanity’s last redoubt. An ocean-borne marvel of massive pyramids and soaring towers, Osiris was originally a refuge, attracting “the world’s most brilliant minds, rich and poor, from the northern hemisphere to the south.” But by now it has passed “from elite technological masterpiece, to benevolent rescue centre, to reluctant tyrant”: the city as we find it is an autocratic place, divided into a wealthy core led by a few established families, governing more or less by hereditary succession, and a western periphery of grim poverty. Our guides conveniently reflect this division. In strictly alternating, sometimes overlapping chapters, we are escorted around the city by Adelaide Rechnov, a wealthy heiress convinced that her recently-vanished twin brother is still alive, and Vikram, a third-generation climate refugee attempting to improve conditions in the west; before too long, the two are thrown together in a you-scratch-my-back plot, and ultimately they begin a more intimate relationship.

There are echoes here of many prior works, but the one that kept coming to my mind was Julie Bertagna’s energetic 2002 novel Exodus. The two books are set in similarly afflicted worlds, and both feature luxurious castle-cities surrounded by refugees, plus paired protagonists from opposite sides of the wall: in fact both the starkness of the premise, and the choice of protagonists, felt familiar in Osiris because they have been so often deployed in recent novels that were, like Exodus, published for young adults. Osiris is not, itself, a young adult novel — not that that would be a problem, but if nothing else the protagonists are too old, Adelaide by a little, Vikram by rather more — but it’s interesting to see the dystopian narrative, having migrated from the adult to the YA category, making its way back again but preserving some of its mutations.

What a bare summary of the novel’s premise obscures is the amount of space Swift creates for her protagonists to simply live in their world and expe...