Here is what we know so far about the cast:
Holden: Steven StraitMiller: Thomas JaneAmos: Wes ChathamAlex: Cas AnvarNaomi: Dominique TipperAvasarala: Shohreh AghdashlooThere are other characters that have been announced, like the important role of Fred Johnson who heads the Outer Planets Alliance (OPA) and will be played by Chad Coleman (Tyreese from The Walking Dead). There are intense politics between the inner planets (Mars, Earth and the Moon) and the Outer Planets (usually known as The Belters) with associated cultural dynamics between people who have grown accustomed to living in space or in limited gravity (Space stations, asteroids, or the Moon) and Earth, which has a huge population and resources but increasingly limited ability to enforce its will on what it perceives as its colonies. However, Mars is almost as (militarily) powerful as Earth and is trying to enforce its will on the rest of the solar system regardless of what Earth may want. The Belters believe they are different from anyone who lives "trapped in the gravity well of a planet" and should be treated as such, the OPA is a group that is trying to advocate for Belters, often using violent means to get their point across.
And then things get really weird when an alien probe (called a "protomolecule") arrives that apparently turns any form of life into zombies. I can't wait to see how SyFy adapts the series, hopefully it will become their "Game of Thrones in Space."