It's a series with a very slow buildup that respect the audience. For an example we are shown the mother of Thomas looking at the nuclear explosion in DC which hints the possible cause of his illness without even making the characters go through a discovery regarding effects of radiation etc. I absolutely loved the ending and there is a the theme that future belongs to those who can change it which is also a personal belief of mine.

I'm currently watching season 3 and things get much better. I think the it'll be one of those stories where you have to watch all 40 episodes to get the full picture.