I really enjoyed the first season of "The Expanse", and leapt at the opportunity to watch the second season when it showed up at the library. This season was 13 episodes as opposed to the previous season's ten episodes.
I thought in the first season that the characters were well done. But now that we're spending more time with them, I'm finding that the writers (the book authors Daniel Abraham and Ty Franck are also the TV screenwriters) concentrate too heavily on one or two traits in each of these people - and the actors are good but not great, which would be required to bring broadly written characters to life. So while each of the characters is very distinctive, they're also relatively shallow. It's better than some author's work, but lacks some complexity that you see in the best stuff.
Having said that ... what they're handling even better than last season is the ideas and the sweeping politics of the entire Solar System edging towards war. The action is intense, the effects are very good, and the politics are well played.
I gave them credit for good science in my review of the first season, but I want to say it again: damn it's good to see space flight handled right. I have to deduct a point for having the proto-creature making noises in vacuum, but I think we can blame that on Hollywood. They even got spacing right (ejecting someone without a spacesuit into space - not that I wanted to see that): no bleeding, no instant freeze, just ... you can't breathe. For added scientific accuracy, Adam Savage (of "Mythbusters" fame) has a small but speaking role in the last episode.
The whole series is a pleasure to watch.