Much smarter than all mangas with similar topic I've read and not so mainstream as majority of manga in general - that's for what I loved reading the subj very much.
I think, the fact that the hero is an adult is really cool. There exist not so many such mangas, that I know (like Monster, Rurouni Kensin, partly Death Note, Gintama...) and it's much more pleasure to read them, 'cause you as reader aren't treaded as 13-year child, plot is mature and not so random and senseless.
