The folks on DeviantArt.com were such a twitter about Black Butler that when I had the CHANCE to watch the entire first season, I knew I'd eventually succumb to curiosity and utilize that chance. Although, I hesitated--I don't do well with horror movies, and I couldn't quite imagine a story about a boy selling his soul to a very dark, savvy demon butler to work out well. Especially because there are so many animes that don't mind being disturbingly violent.
That being said, as soon as I started, it couldn't be stopped. I was taken in, dark or not. Though... I never thought I would laugh so hard, despite the grim subject matter. I constantly found myself laughing out loud! Sebastian is not a demon who's above goofy repeat lines or a good solid pun. He may be out to swallow Ciel's soul, but you really seem to forgive him because he's so fun to watch and so fun to listen to. That and the anime will slide back and forth between a "Hello Kitty" style to something similar to "Vampire Hunter D" so quickly, it will make your head spin or, if you're me, giggle with delight.
That being said--it gets dark on the last episode. I won't spoil anything, but you should know that you might get disturbed by the darkness. And you will probably not laugh, unless there's something wrong with you, because there's nothing funny about it. The last couple of episodes can make you get goosebumps, and the end (which is the 12th episode) will probably slap a frown on your face and it will stay there for at least a few solid hours. Still, I can't take away a star. It DOES *end* solidly, despite the end being a little hard to swallow. I actually had trouble sleeping after I saw it.
You get the treat in Part 2 to learn more about Ciel, more about his parents, more about the contract, and more about his servants and WHY he allows for so much incompetance. Truthfully, I wished there was more. Still, there isn't too much meat on any one episode--they're EXTREMELY short episodes. That being said, they're all very good. But if you think you can just sit down and watch them one at a time, think again, because you would find yourself very unsatisfied if you did.
In fact--my only FAIR complaint is that the beginning title and end title together take up about 6 minutes of every 24 minute episode because no one told them a show's title should only take about 30 seconds... In this season, you'll watch about an hour of title or more. Still, it won't put you off to keep coming back until you reach the grim conclusion. After all, he's one HELL of a butler!