Melissa Scott’s 2023 Fallen is the second book in her Firstborn, Lastborn space opera series. It shares no characters with the first book, Finders, and is set in a different period. More on that second detail later.
The invention of nigh-godlike AIs provided the Ancestors with everything they could have wanted… until they found themselves at war with the AIs. Civilization collapsed. Centuries later, civilization has recovered, although at a lower tech level than the Ancestors enjoyed.
Luckily for the revived civilization, space is littered with Ancestor relics. A few of these relics aren’t existential threats.
Nic en Doroney was indentured to the Novilis family. The deal was that in exchange for sharing the nanites in her blood  with Rejane Novilis, the family would pay for Nic’s education. Having no need for Nic once they sampled her precious blood, the Novilises reneged on the deal. Nic still managed to make her own way in the world. Now she owns and operates the tramp starship Beljaeger.
The AIs were vanquished by exiling them to the possible, the realm through which conventional FTL starships pass. This has the same benefits for interstellar trade as stocking the oceans with kraken would have for oceanic trade. Every trip brings with it a chance of encountering an AI still angry over exile.
Nic possesses several assets that enable the Beljaeger to traverse the possible with less risk. One is an ancient artifact that allows her to communicate with AIs. Each trip, Nic makes a new deal with an AI she knows as Beast. Thus far, Beast has not turned on her.
Rejane Novilis approaches Nic with a proposition. The Starwell is an enigmatic structure on Valenguar. Rejane would like Nic (and her artifact) to tour the Starwell, as part of a project to determine the Starwell’s purpose and perhaps reactivate it. Despite the previous Novilis track record, Nic agrees.
Results are mixed. The Starwell reactivates. However, this provides an opportunity for a political faction, the Newfounders, to stage a coup that Rejane and Nic barely manage to escape. There is a plus side: the couple rediscovers their mutual attraction.
On to the next daring project! The orbital city of Callambhal Above is without power and its orbit is slowly decaying. It had been powered by an AI, but the AI fled during the late conflict. At some point orbital decay will accelerate and the city will crash into the planet below. Rejane has a bold plan to rekindle the power source, one in which Nic will play a central role.
Perhaps the pair will save the city of Nic’s birth! Or perhaps they are dabbling in things with which humans should not dabble, and are dooming everyone.
This is a space opera, so satellites fall out of orbit if they don’t have ongoing power, AIs seem to be more like gods than software, and it’s best not to try to apply orthodox orbital dynamics to the behavior of spaceships in this setting.
While this is billed as the second book in the series, various details such as the timeline Scott provides at the beginning of Fallen make it clear — unless I am misreading the timeline — that this book is set centuries and at least one dark age before Finders. Readers familiar with the history referenced in Finders will therefore be aware that it is entirely possible that our bold researchers might inadvertently snuff out civilization’s light because at some point in their future, someone will do just that.
Worries about the future fuel the disagreement between the Successors (the faction to which Nic and Rejane belong) and the Newfounders. The Successors focus on reclaiming lost Ancestral technology despite the risk that this will somehow allow the AIs to emerge from exile and take bloody revenge. The Newfounders want to create an entirely new technological base. The catch is that there is no assurance that this is possible.
Given their taste for coups and murder, the Newfounders come off as antagonists… but readers know that someone is going to destroy civilization later and may decide that the Newfounders have a very good point.
Given that I knew disaster was coming at some point between this novel and Finders, I couldn’t help wondering if Nic and Rejane were hubristic idiots. Even so, Scott does a good enough job with her characters that I cared about their fates. I’d rate this book as a good time pass.
1: Nic is carrying a nanite burden. Which may be an apt term for the trouble it makes for her.