I'm currently reading (and slowly buying) the Angel Sanctuary manga by kaori yuki. It is amazing, I've been afraid to try out the anime because I heard that it did not do the manga any justice.
Kaori Yuki is an amazing artist and I can't think of one other person whose drawing I love more. My avatar is one of her characters! The characters have such personality and beauty. I read in one of her side notes in a manga book that she is obsessed with beauty... and I agree! and this is a good thing. I am very addicted at the moment and will write a further update when I finish reading the series, I still have a lot to go.
The story is very deep, the characterization is awesome, there is romance, action, and amazing drawing.., what else can I ask for?
Go read Angel Sanctuary :)