It's set in a world with a Dickensian/steampunk feel, in which fallen angels left hell three centuries earlier; their descendants mostly occupy a ghetto called Hells Below, and are an oppressed minority, easily recognizable by their odd pallor and black fingernails. Some of them also have paranormal abilities. They're referred to as Prodigals. Humans government and banks are church-based; bankers are priests, and so are the police, who are called Inquisitors and do in fact torture for confessions. There's also a suffrage movement going on, to enfranchise both women and Prodigals.
The book is divided into two sections. The first is first person, from the point of view of Belimai Sykes, a Prodigal who, thanks to torture at the hands of the Inquisitors, is addicted to a drug called ophorium. Enter William Harper, an Inquisitor who needs Sykes' help. Harper and Sykes have a sexual relationship (all fade-to-black) and also begin to develop a working relationship. The second section is third person, and I found I missed Sykes' ironic voice; however, the author used the pov to give a more nuanced view of Harper and of Sykes as well. Their relationship continues to develop in the second half, and there was some Francis Crawford of Lymond-esque angst for Sykes which amused me greatly.
In short, I liked it, and wished it had been longer, to more fully explore the world; also, I wished that the novel had more sex scenes. That is, more than one brief one. Why yes, my prurient interest was roused! And I felt that sex scenes would have been a way to more deeply explore the differences and similarities between humans and Prodigals, as well as between the two men, whose actions throughout spoke louder than their words.