I've read a few reviews that say Gunparade March is a poor anime, that the issue of the alien invasion doesn't have enough investigation into it, that we are left unanswered. The reason is because although containing giant robots, this isn't a Mech Anime similar to Evangelion or Gundam Wing, the alien invasion is at most a sub plot, and the main story revolves around a class of teenagers ' lives, as they try to live around the aliens. The series is actually a drama/ slice-of-life. Unfortunately the box cover and DVD description doesn't portray this, and makes it seem like an action based Mech shooty anime, so I assume this is why it gets some poor reviews. But, if you keep all this in mind then chances are you'll enjoy it!