I'm going to be truthful here: I liked this anime, a lot. But I can't be clear on why.
The story was good. I mean, parts of it were REALLY good, and parts of it were... confusing at best. I didn't know what the main plot was about until 5/6 episodes (I don't remember exactly). While interesting as a mystery show meanwhile, it didn't really caught my interest until the main plot was revealed. Afterwards, I was quite hooked. So I gave it a solid 8/10.
The art was the thing that drew me to the series in the first place. It's very pretty, to be frank, and I might be falling short with an 8/10. I really liked the character designs.
The sound was quite interesting in itself. It complemented the show very well. Another solid 8/10.
The characters... I'm not sure. While maybe I'm not a fan of Sebastian, the other characters are well developed. I particularly enjoyed the stories of the Ciel's staff. Each of them had a short but interesting back story. A 7/10 is fitting.
Enjoyment, 8/10. Like I said, I didn't really became hooked until after the main plot is shown. Otherwise it was really enjoyable, except for a few moments of unnecessary shota undertones. I'm not really interested in that and found it a bit creepy sometimes. I might be biased though, because, after the art, the thing that made me watch it was the dark Victorian-age London setting. I loved it.
Overall 8/10.