Another entry in Hunt's steampunk/what-all series (The Rise of the Iron Moon, 2011, etc.).
Ice-covered and only marginally habitable, surrounded by a magma sea, the island continent of Jago is the only place where electricity works. Emigration is forbidden and most of Jago's underground cities are abandoned. When young Hannah Conquest, a Jackelian by birth, was orphaned, Archbishop Alice Gray of the Circlist Church—another Jackelian exile—took her as a ward. But even Alice is helpless when the Guild of Valvemen's evil leader, Vardan Flail, conscripts Hannah. Despite their skill with electricity and computing, valvemen rapidly develop hideous deformities due to radiation. Worse, when Alice is brutally and mysteriously murdered in her own cathedral, somebody also tries to kill Hannah, evidently in an attempt to suppress a secret kept by the archbishop and presumably passed to Hannah. Perhaps the death of Hannah's archaeologist parents shortly after her birth was not accidental. Meanwhile, in the Kingdom of Jackals, Jethro Daunt, a defrocked Circlist parson turned private investigator, and his sidekick, a sentient-robot steamman named Boxiron, accepts the Circlist Inquisition's request (read demand) to investigate the murder of the archbishop. This relatively sedate beginning swiftly accelerates into typically frenzied action and mind-boggling invention involving duels, gods, assassinations, battles, intrigue, cryptography and dangerous secrets: Hunt sets no limits on anything, which is both the attraction and the problem.
A slow-starting murder mystery that rapidly turns hyper-complicated and explosive, though for many readers the series remains very much an acquired taste.