I've always been a bit of a sucker for a "space drama". From the idealistic Trek series' to the gritty Battlestar Galactica, the "soap operas in space" genre is one that appeals to me most of the time. When it comes to the first season of The Expanse, however, I'm pretty much split right down the middle: On one hand, I really enjoyed the world-building being done and the universe being created. On the other, there wasn't nearly enough mystery or intrigue to keep me completely engaged each and every episode.
For a very basic plot summary, this first season plays out somewhat like a mashup of BSG and "Blade Runner":
The BSG element sees a space vessel crew, led by Jim Holden (Steven Strait), witness what amounts to an act of space terrorism. People of Earth and people of Mars are fighting, and the "belters" (basically slaves) are caught in the middle. When Holden and crew witness the event that could prove catastrophic to the war, they are pursued from both sides (Earth/Mars) for the information they possess.
At the same time, police officer Joe Miller (Thomas Jane) is trying to track down a missing persons case, that being Julie Mao (Florence Faivre). While at first seemingly a waste of his time, he quickly becomes invested in her mysterious disappearance and figuring out all the intrigue it potential holds.
To be honest, that dual-plot summary brings up my first issue with this inaugural season: it feels like two different shows in one at many points. Though I understand the point/goal, as both threads are indeed brought together in the end, that convergence was ultimately not all that satisfying, meaning it felt like two potentially interesting narratives were getting short-shrifted for very little payoff.
Not helping matters is a plot line involving political figure Chrisjen Avasarala (Shohreh Aghdashioo). I never felt like I understood what her role in everything once. That could be a "me problem", of course, but when her plot was front-and-center I would often find myself checking out a bit.
Like I said, this first season does a good job of setting up the universe and its conflicts. The war between Mars and Earth is an interesting concept, with seemingly much to explore. Also, most of the characters have interesting personalities (if sometimes prone to wandering a bit, script-wise). Put it this way: where at times I felt confused or a little bored, the overall structure kept me from checking out entirely at any point.
Without any outside knowledge, this is a show I probably wouldn't ever come back to. However, I have heard that it really picks up in the second season (general rankings confirm this), and the third might be even better yet. So, I'll probably end up giving it another opportunity at some point, especially with the S1 finale setting up a legitimately interesting plot point for going forward. Strictly as this first season goes, however, I'd consider it pretty average (maybe slightly above) sci-fi fare.