I read the manga first, so I guess I am pretty biased. However, I really just don't think that the anime was as good as it could have been.
First off, it was much too short. Yes, short animes are always fantastic, don't get me wrong - but in this case, I wouldn't have minded watching another 30ish episodes.
Second, it didn't follow the manga very closely. Sometimes it's better not to follow it exactly, but in this case, it made the story confusing for me. I feel like they cut out so many important factors that it just didn't work.
The animation was pretty good, but it didn't make up for the lack of a sturdy plot and the confusion caused cutting out 9ish volumes of information from the manga.