Majestrum

Henggis Hapthorn, foremost discriminator (detective) of Old Earth in the far future time of the Archonate, has a problem. Well, perhaps a series of problems. First, there are his cases that may have something to do with a plot to overthrow the government, but perhaps even more troubling is the impending return of a time where "sympathetic association" (i.e. magic) is ascendant over scientific rationality. This problem has been made peculiarly personal for Hapthorn as he shares his brain with another persona, born the magically separated intuitive part of his psyche, and his integrator (a personal AI device) has been turned into a cat-monkey creature familiar. As one might expect, Hapthorn's personal woes and his case are not as separate as they might seem, and he will have to confront further magical forces.

The return of a time where magic works is familiar from games like Shadowrun and Rifts, and even kid's cartoons like Thundarr the Barbarian and Visionaries, but what none of those have is the placement of an ultra-logical, far future Ellery Queen, trying to oppose the coming paradigm shift, which has become a fairly personal affront.

Hughes's universe and his writing style are in a Jack Vance mode. His setting of the Archonate and the Spray resembles Vance's Oikumene and Gaean Reach. It makes his Hapthorn tales something like if Magnus Ridolph or Miro Hetzel was confronting the dawning of the Dying Earth. There is plenty of stuff to borrow for a Vancian science fiction game, or inspiration for a whole setting.

Majestrum is the first Hapthorn novel (though based on how it opens, I suspect some short-stories predate it). There are three others and a short-story collection, all pretty cheap for Kindle.