This is not your normal anime, and it's fabulous. I was hooked from the first episode (though my brother took ten or so episodes to get into it, and then only through my prodding).
The story line in this anime is incredible - it's well written, secretive, mysterious, right up until the very end. Like a novel, the story keeps expanding. There were such highs that I was literally on the edge of my seat in anticipation, and lows which gave me a chance to catch my breath. The characters are consistently surprising, and also surprisingly human. There are no righteous characters with a tragic flaw that they must overcome, nor are there ultimately wise characters who can see the end of a situation. Perhaps that's why I enjoyed this anime so much.
The charcters develop soundly, along with the plot, leading you ever further deeper into this mess of a world presented in the anime. And, though it may be long, it's definitely worth the trip!
However, I would never suggest this anime for children. I feel that this is far too intense for children, and some of the moral questions raised can be a little disturbing. In fact, there are times when this anime was disturbing to me.