This game was a surprise gem for me. I checked it out only out of curiosity, but never thought I'd play it much. To my delight, it is a really fun game. It also looks really good, which, of course, is no surprise for Shin'en.
Anyway, for those who have yet to check it out, I highly recommend it. If I had to categorize it, I'd say it was an action / puzzler. Not terribly difficult, but still a good bit of fun.