Kuroshitsuji was what drew me back into the world of manga after my short three year reprieve. Art wise, it utterly appealed to my sense of aesthetics, but as I've always said, art is entirely subjective; so clearly what might me a perfect masterpiece for me, might be something else for someone else. However, if my opinion matters however much, it was dripping with gorgeous scenes, the evolution of art, though, is certainly obvious, As it is, Yana Toboso's style had grown more refined, and delicate in the later volumes as compared to the first. Nonetheless, we have stunning eye candy with exquisite wardrobes, and scenic views from the get go.
Regarding the characters themselves, for I place plenty of importance on character development as opposed to plot, Ciel, in my opinion, is the perfect protagonist. Controversial, no doubt, but I do so tire of those pure, earnest do-gooders... The selfless, innocent, naive heroes, I have naught against them, but I do enjoy a taste of bitter sweet after all the sugary goodness. Ciel may not be morally upright, but in that sense, he behaves like a human. Humans aren't morally upright; even if we assume we are, when it comes down to it, we take care of our own. If we didn't, our species would have been wiped out eons ago. Ciel is a human. As much as I adore Manga Characters, and I adore them lots, I relate to humans better.
Sebastian is a demon. I've really not much to say about him, because there's really not much to say. He does brilliant work, looks like a dream, and assumes a rather mysterious contradictory personality. The thing I love best about Sebastian, is actually his relationship with Ciel- they often bring out the best and worst of each other. Ciel makes Sebastian less of a demon, and Sebastian makes Ciel less a human (that being easily corruptible, self-centered and greedy). Either way, they've admirably interesting relationship dynamics.
Plot-wise, I love it all, save maybe, the arc after the circus, it seemed to drag on too much for a bit, but it was nonetheless a refreshing change to watch our main duo from a third party's point of view. My current favourite remains the circus arc, it sent chills down my spine the first time I read it, and it still makes my heart flutter every time I decide to revisit that plot. The irony of life and the inadequacy of humanity was so well woven into the plot, it just made me smile.
The zombie arc was a nice action-packed bit, and it had a nice pacing too it, it didn't seem too rushed, nor did it seem dragged out; and we got to see Ciel's first-class manipulation skills, it just made me fall in love with him more. As for the current school arc, the premise is certainly noteworthy. Clearly, there are those who detest the apparently overused setting, but I would say, I'm leaning towards the supportive side. However, I reserve to make judgement, as there's a wealth of unseen potential.
Overall, it's a beautiful manga, (with several historical errors, but I'm not quite the nit-picky sort over factual details like this), and I would give this manga two thumbs up. I would give ten, if I had ten thumbs. A hundred, if I had a hundred. And yes, a thousand if I had a thousand. So on and so forth.