Faction Paradox: Of the City of the Saved... (Faction Paradox series)

Laura Tobin's a private investigator who's summoned to investigate a very peculiar murder --- one that occurs in The City of the Saved-a haven at the end of the Universe, populated by every human being or pseudo-human being who's ever lived. Except that in the City, all murders are literally impossible. But Laura's got a very dead body to prove otherwise. As part of her investigation, Laura will come across the machinations of the various powers within the City, including the Rump Parliament and the City Council and more --- and also perhaps the Secret Archiects who built the City in the first place. And then there's Faction Paradox, a group of time-travelling ritualists, saboteurs and subterfugers -- essentially, the criminal-cult to end all criminal-cults. As always, the Faction's trying to subvert history to its own ends, preferably by letting its rivals kill each other off, then swooping in to seize whatever's left -- presuming the Universe survives the conflict...