The Warded Man

I'd read Howard Taylor's blog post at Schlock Mercenary about The Warded Man, so I decided to give it a try. It's a standard fantasy world, with medieval technology, basically European / American culture. The difference is that demons materialize out of the ground every night and attack anyone who's not in a warded enclosure. Generally the only people who travel any distance are highly paid Messengers, who put wards in a circle on the ground but still sometimes come to a messy end. The book tells of three children who grow up to be young adults, and how they deal with this state of siege. The characters are interesting, and it's a good first novel.
The main problem with it is that the background doesn't feel realistic. There are five cities, of which one is pseudo-Arab and the rest are Generic Fantasy Culture. Each city has one main economic resource--there's the Forest City, the Mining City, etc. The villages are separated by several days travel, which is why the duchy has daring Messengers to travel among them--but why are they spread out so much, other than to make Messengers necessary? In the Middle Ages, settlements were usually separated by half a mile to two miles, and there's no obvious reason that they couldn't be in this setting as well. And if there was a reason for the villages to be spread out, why don't people build warded inns or forts close enough that no one has to sleep on the road? We discover that a ward has to be uncovered to be effective; its power can be blocked if mud gets on it, or even if a leaf falls on it. Aren't any of the demons smart enough to kick some dirt, throw some mud, toss a tree branch?
It's worth checking out of the library, although I don't think I'd buy a copy again.