If you follow the comics, you know who Legion's father is and why he is so powerful. His parentage is hinted at in the first season but never outright given away. The season is mostly centered around fixing what David has always assumed to be a mental illness (paranoid schizophrenia, to be exact). Still, as we find out throughout the season, it is a combination of his powers manifesting and something else. It is a trippy show that is hard to follow (especially on the first viewing), jumps around a lot in the story, and just gets weird at times. That said, it is very well written and acted, and it makes sense after a while. Plaza steals every scene, and she takes advantage of the opportunity to ham it up when called for (which seems to suit her personality). Stevens and Keller are great in their roles as lovers who cannot touch each other (because she switches bodies with whomever she touches). Jean Smart is great in a Professor-X-like role as the mentor for the group. There is also the requisite shadowy government organization trying to hunt the mutants down, playing one of the antagonist roles.
The Blu-Ray set is a two-disc set, and the show (which has a lot of special effects) looks and sounds great in HD. It is a very visual show, so the high-definition format really pops. The extras include deleted scenes (about a half-hour's worth) and several behind-the-scenes and making-of featurettes. Good for what is there, but not too extensive. The show packs a lot into the 8-episode first season and sets up the recently aired second season well. If you are a fan of the X-Men comics or movies, it is definitely worth checking out.