I think it's a little unnecessary because, well, if you didn't play the game, you won't understand the half of the anime, buuut, it's pretty cool for the fans :,D. (sorry for the bad english)
It can't keep my interest. I loved the game but the anime is lacking. I think part of it is the fact they skip past most of the palace which is a huge part of the game and they don't actually come off as phantom thieves because of that. I know they have time restraints but I think the series suffers from that. There are probably other things too but I just can't put my finger on it.
There are some very cute moments, but the animation really throws me off. Also is annoys me a little that they have done Makoto's confidant but not Ann's, so unless they are pushing Ren x Makoto...I wouldn't mind that...I don't know why they would choose to do this.
I'll tell you when it's over. Not entirely sure yet. Though it's not quite as good as the P4 anime, though the dub may change that in all the wrong ways like Danganronpa 3 anime did.