I loved Kuroshitsuji so of course I decided to watch the second season. When I did watch the first episode of the second season I was a bit pissed and disappointed because they made it seem like this would not be about Sebastian & Ciel. They totally tricked me! I devoured these 12 episodes within one day. If you liked the first season, you will absolutely love the second.
I feel like I liked the second season a lot more. They made it way more entertaining by adding in another master/butler pair. By the time I finished the 12 episodes, I wanted more. The way it ended for Ciel & Sebastian in requards to his soul, I didn't like. But the way it eneded, like the first season made me want more. That may be wishful thinking, but a girl can dream.
Kuroshitsuji II is definitely darker than the first season, but that works out good. The only thing is I wish that they would have expanded it a little bit into more episodes, just because I cannot get enough of this anime! I highly recommend this anime.