Black Butler is an ongoing manga that isn't a big shonen brawler, so naturally the anime situation is kind of wonky. The latter portion of Season 1 takes its own route and abandons the manga, much like the original Fullmetal Alchemist series did. As a result, Black Butler II is completely removed from the manga, and was created to build upon the success of either Black Butler Season 1 or the manga itself.
Now what about the plot? Wasn't the ending of Black Butler pretty solid, to the point where Ciel shouldn't even be involved? Yeah, it was, and this is no spinoff; It's a direct sequel to Black Butler season 1. Without spoiling the transition between seasons, this season focuses on the rivalry between Ciel and Alouis, who both work as the Queen's underworld dogs, as well as the rivalry between Sebastian and Claude, who both fight to acquire the souls of the boys. If you watched Season 1, you pretty much know what you are in for in terms of content, as Sebastian and Ciel solve cases and get into big otherworldly fights, just as they did last season. All in all, I felt that the premise and execution of the season was pretty solid, but it wasn't without it's flaws. When trying to rectify the ending of season 1and transition that into something workable for season 2, the show can get a little sloppy, but I feel that it all works out in the end. The season's plot, while not incredibly strong, is still enjoyable enough to keep me entertained throughout all 12 episodes.
Visually, Black Butler is pretty pleasing. I'm reminded of how I'm glad that the show made it onto Blu-ray every time that I see some fine detailing, like the fibers in a curtain, or the details on a canvas painting. Colors and lines are quite vivid and clear, and the animation quality is pretty high. Certain scenes really stand out because of their grandiose nature of many of the fights in the series. I still can't get one particular scene out of my head; It starts off with Claude tap-dancing to some tension-inducing orchestral music, and turns into him arranging the dining room in the floor below in the most over-the-top way imaginable. When I saw it, all I could think about was how damn cool it was.
To wrap things up, I think that Black Butler II is a fine purchase, especially if you are an extras junkie like me. In fact, I neglected to mention some of the other Extras, that include a blooper track (that the Japanese often forbid from being included, from what I have heard), and some trailers for the show itself. I actually ended up watching it twice in a row, which is pretty unusual for me, so I definitely feel as though I got my money's worth.
(On a final side-note, I bought the Limited Edition of the set, which comes with an extra wide box so that the Black Butler 1 Blu-ray would fit inside of it. Personally, I'm a bit annoyed by that, since I bought Black Butler on DVD, and it had its own limited edition box. It wouldn't be so bad, if 2/3 of the limited edition box weren't essentially empty.)