Despite this being almost exactly what steampunk isn't, for some reason this has a very steampunk feel to it, possibly the mental picture of the Clarrissa Stark character in her thick goggles. Instead of the idea of a Victorian Britain having made some scientific advances early, what we have here is a story with no real anachronisms, just a normal Victorian missionary finding himself somehow transported to a strange alien planet and trying to make sense of it.
This is an old-fashioned adventure in a couple of ways. Firstly it concentrates on making a world that is self-consistant rather than one that is entirely plausible in strict scientific terms and is no less enjoyable for that. So it is a bit like a classic SF story from Wallace or Wells.
The other way it is old-fashioned is that it is framed as the discovered journal of the hero, and therefore entirely written in the first person. This sort of device, with its little preamble about how the document found its way to the author can be annoying if done badly, but in this case it works very well.
I have to confess that I hadn't heard of Mark Hodder before, but after this I will certainly be downloading a few of his other books.