Story
The story itsself is captivating from the very beginning. The whole time I kept wondering what was going to happen next. There were things I would have never expected- excellent plot twists- and even a smidge of humor for good measure. It's got the right balance of everything: Horror, Angst, Romance, Drama, Comedy. It has it all.

Art
The art was beautifully executed. Each major plot scene gave just enough imagery to make it not too gory or not enough. Again, it had just the right balance. Also, there were some different angles thrown in there to make it that much more interesting.

Character
Characterization was amazing. I kept thinking I knew these characters' motives inside and out, and then they'd surprise me completely. There were so many twists and hidden agendas you just couldn't help but want to know what they're going to do.

Enjoyment
How could I not enjoy this manga? It's absolutely amazing in every way. It's one of those mangas that you just can't put down and has you begging for the next installment. It's very thrilling to watch it all unfold.

And as far as I've seen, the anime is just as well executed.