The Affinity Bridge by George Mann can easily be called a blend of Urban Gothic, Detective Fiction, and Scientific Romance into the milieu that becomes Steampunk. Mann, who is the head of a major British SF/Fantasy publishing imprint, takes tropes from each of the three aforementioned genres, and has a grand old time twisting them into one mystery after another.
Sir Maurice Newbury and Miss Veronica Hobbes, his brilliant assistant, are charged with the tracking down of an escaped automaton, the investigation of a series of strangulations attributed to a glowing policeman, and oh yes, the plague of revenants ravaging London's slums.
Newbury himself is a detective in the vein of Sherlock Holmes -- brilliant, logical, fascinated by the new steam technology spreading around England, and slightly addicted to drugs. Of course, the Holmes enthusiasts among us will correct me that Holmes wasn't actually addicted. He merely experimented.
The story itself is in 1901 London, with airships and other steam-powered and mechanical innovations spreading quickly around the nation. Queen Victoria is kept alive by a rudimentary life support device of bellows and mechanical workings, and is still very much in the thick of the action. Newbury acts on her orders and hers alone -- as an agent of the Crown he goes where the Empire wills him to go. And Hobbes follows behind him, partially to help, but also to make sure Newbury remains a loyal servant.
The "affinity bridge" of the title is a link that allows for transference of a human consciousness from a living person into one of the story's ubiquitous automatons. Newbury and Hobbes uncover the secret behind this act in a factory belonging to some automaton makers, who are also connected to the plague revenants (zombies). We have Urban Gothic from the fog of the slums and the "hidden city" therein, the Detective Fiction piece from Newbury and Hobbes' investigations, and the Scientific Romance from the dark use of technology in the form of the affinity bridge.
Perhaps the most interesting thing about this novel is that it ends up being very Victorian in language and grammar. It's a fascinating choice for Mann to make, and one that actually ends up working quite well when you get into the swing of the novel. Mystery, action, science, and a breakneck pace ... what more could you want?