I remember enjoying The Necropolis Railway very much when I read it a few years back, and my current search for new detective writers led me back to his creation, Jim Stringer in this, the second of what has already become quite a lengthy series.
While I do enjoy the books very much, I do quibble a little about whether they truly qualify as "detective" fiction, at least the two which I have read to date. They are really just well-written narratives featuring a railway fireman who fancies himself to be also a detective. Whether he really is must remains a matter of conjecture. He takes part in no structured investigations, frequently leaps to wild conclusions, and is almost always wrong.
However, none of this seems to matter. He and his wife are likable and well-drawn characters, and the narrative is strong and well paced.
The author obviously has a love for steam trains and all the period and technical detail is spot-on. What is even more impressive is that the books are written in the first person, and reveal a narrator who is instantly credible, with period dialogue and perceptive inner thoughts.
I think what makes these books so endearing is that both the central protagonists are so essentially decent that it is impossible not to like them, and to care about what happens to them, which is more than one can say for Never Apologise, Never Explain, which I also read recently.
By coincidence, I happen to be following The Blackpool Highflyer with The Railway Detective by Edward Marston, of which more shortly.