I am looking for a short fantasy novel that centers around a young man who meets an older man who knows how their "Edwardian" world really works. The fantastic creatures, which haunt the world at night, are actually machines, built underground and recharged each day. The world was an extremely dangerous one at night, and the older man possessed a cart which was drawn by horses, I think, but which could be self propelled if he needed to escape the monsters.
At the end of the novel, a female journalist meets the two guys and threatens to write a story revealing the existence of the world to the rest of the galaxy. There is a really good scene involving combat with a half-finished mechanical dragon.
I cannot remember the title or author. It was a book from a thrift store which I read at least ten years ago. I am pretty sure the cover had been removed.