"30 Days" has a couple of flaws, but it's an involving read.
The writing is excellent, I think, well-suited to the medium. The concept is wonderful and certainly Niles doesn't spare the gore or pussyfoot around the concept of vampires ripping open throats. He puts in some disturbing imagery and his plotting is close to immaculate.
A moment to address the other reviewer's complaints about cliche: Yes, you're right. Now stop whining. I doubt much new can be done with vampires, and it's great to see the human battling with the throat-ripping beast without having to deal with Anne Rice's sexual peccadilloes or purple prose. If Lestat actually existed, I would have purchased a flamethrower for the sole purpose of shutting him up. And maybe I would have taken out that whiny Louis, too, while I was at it.
All praise and defense aside, I suspect Niles was given three issues instead of the four he asked for (or perhaps the four he should have written) and as a result his character development is lacking. While I think it's great the book hits the ground running, we only really get to know Eben and Stella, and those two we don't know very well, in the end; the townsfolk have maybe a panel or so (few are granted names) and then get turned into hamburger.
The art isn't to my taste; I think the murkiness enhances it quite a bit, and there is some absolutely beautiful work with what I believe to be watercolor, but I don't think it would have killed Templesmith to be a bit more traditional and realistic. The sheer beauty of some panels, especially that opening splash, is absolutely frustrating next to the sloppiness (which I suspect was intentional) of others. Still, I'll cheerfully grant that it suits the story well.
Overall, it's quite a fun read, a little too quick but definitely worth reading. I suspect the movie will be better, though.