I’m about three quarters of the way through the book I’m reading, which is a young adult fantasy novel.  I’ve noticed all of a sudden an abrupt shift in not just the pacing but also the level of world-building.  The characters have gone from being in a country setting into an urban environment, and where the former was described very sparsely, the latter is full of a thousand descriptors and all sorts of things to make the setting feel as vile and gritty and real as possible.  Oddly, rather than make the city feel real, as though it is a place the author and the protagonist both know well, the myriad descriptions of the sickly people and their diseased lifestyles and the general air of melancholy pervading the city make it seem unconvincing, as though the author is trying too hard.  Conversely, the straight-forward descriptions of the countryside, which are spare and brief, have the opposite effect, as they seem to be such through confidence on the author’s part–he knows these areas, and it is assumed that we do, too.