This is an amazing story. Yes the artwork isn't all that much to my taste, though I got used to it after a few episodes, yes there are plot holes, yes it starts slow. I don't care about the above to be honest. The story is gripping, the characters really well developed, I cared for them, though I'm old and cynical. And there are more twists in the plot than in the local roads in county Kerry! Nearly all an entertaining surprise.
It's not a tale for cretins though, it can get nerdy and convoluted, and something which nobody mentioned, it's fairly deep philosophically as well. You can just watch the story and run away with it but there are questions all along the way, important questions. Who or what are we, what is reality, what is illusion, what is perception and what link has it on reality ....also there are great lessons in life: we CAN change, for the better or the worse, regretting the past or fearing the future will ruin your life, be brave, don't give up, so on. I have the feeling there are some references to Buddhism in there but I'm not familiar enough with it to say more. This series I thought was very intelligent, and is not necessarily aimed at teens, on the contrary there is something in it for every generation.
As usual I thought the American dubbing was a disgrace, (what I heard of it, I always watch in Japanese - excellent voice acting there, if clearly shaky subtitle translations) and only Crispin Freeman who dubs Karasu appears to make some sort of effort and have a clue on how it should be played. I'm not sure I could have stuck with more than one episode in English.
Oh yes, and the soundtrack is brilliant.
8 out of 10, and I will watch it again, knowing what I know now, I need to watch it again. Besides I miss the characters already. Minus some bad art IMO in places, this is one of the better series out there, right up with the better known usual ones. I can't recommend it enough if you like to use your brain while watching entertaining TV.