The second season continues to follow the Rocinante crew and Undersecretary Avrasarala in separate storylines as they deal with the discovery of the alien "protomolecule" that has been loosed on Eros and threatens other parts of the system. Detective Miller joins the Rocinante crew, merging their plots, and opening up some narrative space for a new one: the adventures of Martian marine Gunnery Sergeant Bobbie Draper (Frankie Adams) and her squad. Later on in the season we're also introduced to Praxidike Meng (Terry Chen), a botanist who is searching for his missing daughter and crosses paths with the Rocinante.
Aside from "Game of Thrones," I can't think of another series out there right now with such a grand sense of scope. "The Expanse" continues to have its maneuver its characters so that they're always in the thick of the action, but clearly larger events are happening around them that are being driven by outside forces. To help show different sides of the story, there are frequently little digressions with minor characters, some of whom become recurring, some of whom are simply one-offs. The first season also did this, but in the second season there's much more to keep track of - characters, locations, concepts, and organizations. It also requires considerable patience to wait for some things to pay off. Bobbie Draper, for instance, is introduced in the series opener but we don't have any sense of why she's important until halfway through the season.
On the other hand, there's a much better sense of direction and cohesion this year, now that the "protomolecule" has been revealed to most of the characters and we can see how some of the big pieces fit together. I especially enjoyed the way that the little maneuverings between Earth and Mars were pushed more to the forefront this year. Avrasarala remains my favorite character, and I still don't think that she gets enough to do, but giving her some better baddies to bounce off of and some bigger crises to manage really helped. I'm also much more invested in the Rocinante crew, now that we've had the time to get to know the individual members of the crew a little better, and Meng has joined up - he's easily the most sympathetic of the bunch right now.
A few years ago I complained that American television was suffering a dearth of spaceship series, and that's largely still the case. However, "The Expanse" makes for a notable exception, which really helps it to stand out from the crowd. It's a little old fashioned in the way some of the stories play out - Miller notably follows a particular set of romantic old genre tropes all the way to the bitter end - but its commitment to hard science and epic storytelling remain very refreshing. I continue to appreciate the way it pushes boundaries, especially related to casting choices, and how it doesn't bother with much hand-holding. While not especially prone to technobabble, the exposition is dense enough that it's good to have some nerdy leanings to really enjoy the show.
I'm looking forward to subsequent seasons, especially now that the series seems to have found its groove and feels more sure-footed. Several bad habits have been curbed, and the writers seem to trust that their characters can carry more of the weight, which is going to be vital in the long run. There are still a few shoes in the air that really need to be dropped sooner rather than later - we sorely need to get Amos's backstory squared away - but I'm satisfied that the show's creators seem to have a good handle on where the show is going.