I've watched this series, from start to finish, four times. Each time I appreciate it more. As two of the other reviews note, it is not an action story. Instead it's a mystery (a very dark one) with a mix of love (romantic, familial and platonic), and the mix is balanced quite well. I also agree with one of the reviews that it would have been nice to have had more but the 26 episode format may have been too much.
All-in-all, I would recommend this for those looking for a story with excellent character development, depth, and good voice acting (Japanese, since I don't do dubbed).