While this book did have a few genuinely unsettling moments, there just wasn't anything particularly noteworthy or compelling here. As I was reading this book I kept thinking how similar to Stephen King's "The Mist" it seemed... then one of the characters actually asked if the other characters had seen "The Mist" movie. The main difference between "Darkness on the Edge of Town" and "The Mist" is the origin of the darkness/mist. That was a little too derivative for my comfort.
There is no subtlety of characterization, and most of the characters are wooden, uninteresting, and/or cliche. The young "hood" kids' dialog wavers between kind of funny and almost painful, and Christy, the main female character, behaves totally incomprehensibly and inconsistently. (The only other important female character, incidentally, is practically a carbon copy of the religious female antagonist in "The Mist".)
The main character, Robbie, seems like he might have some sense and might be on to something by trying to study the darkness, but he doesn't try very hard or take intelligent action based on the information that he is given. When he realizes that the runes that Dez drew are effective at keeping the darkness at bay, the first thing I thought was that he should try copying the runes and throwing them into the darkness to try to drive it back, but it doesn't occur to Robbie at all. Although he does have the sense to ask Dez about the runes, it also doesn't occur to him to study the books that Dez has to see if he can find a solution. It doesn't seem to occur to anyone else in the entire town to try to seriously investigate what is happening. Rather, it seems like the details about the origin of the darkness were there just for the reader's information and to squeeze some Lovecraftian lore in, not because they really mattered to the plot--it certainly didn't seem to matter much to Robbie.
I think there is a compelling story in here, but it isn't the one that Keene told. Dez's background story describes how he used to fight demons/malevolent entities, and he and his group sound like a Buffy-like group that failed and fell apart. I think his perspective through that lens would have been much more interesting.
It's an easy, short read but lacks any depth at all. I kept reading mostly hoping for a payoff that never came. Meh.