I liked the game a lot but yeah, coming from a fan of the series I guess this doesn't mean much.
I would say... The game overall is very samey, in the sense that all you do is battle, explore and fuse demons. If that kind of gameplay loop didn't grabbed you the first time, I'll doubt it does the second.
I was really liking it, but sadly had to drop it because of some issues I was having with the PC port. I was enjoying it tho, game had it's fair share of humor and the battle system's fun and overall very original, which I always aprreciate. Guess I'll try in the future, maybe on another PC or just emulating the PS3 version.
Oh and yeah, Iron Sky is a movie about space nazis. Kinda bad but kinda fun, if you are on the mood of a bad but wacky movie.