This two-season anime is written by Urobuchi Gen, and plays out with some similarities to Gundam: Earth fights human invaders from space, represented by a bunch of kids taking on a series of mecha with special powers.
The first season begins strongly, with intelligent fights that draw upon physics, sudden deaths, mystery, drama, and a personal experience of the war. The storyline is straight forward and suffers from Slaine’s thread going off on a tangent until a rather extreme twist.
The second season falls into a much less interesting formula, with the dramatic finish substantially reversed, and episodes generally consisting of the enemy mecha of the week being defeated by an increasingly invincible and aloof protagonist. There is a build-up towards a finale and some potential high drama, but this is wasted in a damp squib of a climax where the romantic subplots evaporate too.
The animation and early writing is nice, but Aldnoah Zero is best enjoyed with low expectations.