Been watching this show since E1. Not bad at all. I got interested after E1 and decided to read the novels as I'd never read Charlaine Harris before. They were enjoyable. Nothing spectacular but pretty good. There are 3 of them: "Midnight Crossing", "Dayshift" and "Nightshift" in that order if your interested.
So far the show has stuck pretty much to the original story lines. Although they have changed or eliminated a couple of characters. e.g. In the novels Lem the Vampire was a white guy.
The story line at the moment is about halfway through the 2nd novel. The novel story line ended at the end of #3. But, it ended in such a way that nothing precludes carrying the story further. Kinda "happily ever after sort of thing".
The ratings look very good so far. Which makes me wonder if we might not be seeing this show again next fall as a full time series rather than a limited run summer event series.
Frankly, I think this and grimm are the only shows NBC has put on in the last several years that are worth a crap. But, that's just me!