The Manual of Detection by Jedediah Berry

Jedediah Berry's first novel is a firecracker of an old-fashioned detective story, done steampunk style. The story centres on Charles Unwin, a quiet, methodical clerk whose job is to write up and file the reports of Travis Sivart, the dashing, cigar-smoking detective to whom he is assigned at "The Agency". Then Sivart disappears, Unwin is unexpectedly promoted to the detective's job, and when he goes to complain to the chief of staff that the promotion must be a mistake, he finds his boss dead in his chair with a mysterious record playing.