Plot/Story
I think the story is quite original; it is about people who are able to create or produce a barrier whether to protect or to imprison an object. The story is focused to supernatural tales and myths around the world, especially in Japan. What makes it interesting is the way the author elaborates what Kekkaishi is and how the world in the manga works differently. You must read it from the first chapter or you'll never get what I mean with my limited explanation, but I assure you, you won't regret it.

Characters
The characters are having quite development; many things happened and changed the course of the story, including the point of view of the characters. Like mystery, readers aren't aware of the true intention of each character, but the author keeps the pace to reveal the secret. Along the road, there always be some kind of option whether we are to like the character or not.

Drawing Style
Despite the advancing story and strong characterization, I'm not much of a fan of the stiff and "mistakenly put" expression of the characters. It looks like the author really enjoys drawing with long lines and simple designs. It is not a bad thing -honestly speaking, that's one of the reasons why the manga is quite distinguishable- but I wanted to see something different.

Enjoyment
I'm pretty much enjoying this! I always wait for the releases, but the long scanlation hardly offers more satisfaction.

Overall
A must read. I don't think you can find an interesting, original yet familiar manga like Kekkaishi anywhere near our time, but then again, this is only personal review. Compared to big shot like One Piece or Naruto, the manga isn't a kind likely to catch large number of readers but only for alternative, which might be the reason why the manga isn't too notable in the origin country.