LOVE The Expanse.
I have read all the books (and the novellas). Big fan of "The Churn;" for all you Amos fans...
This was a very reasonable adaptation of the fourth novel-- I was kind of surprised they chose to do it, because it is the weakest of The Expanse works. And, quite frankly, they could have jumped right over it. It was, however, as it was written, the easiest to adapt into a movie/series. Chibola Burns is a stand alone Western-ish adventure. Murtry is a bad dude and a believer. Way bad and scary in the novel. They portrayed him well-enough. They also dumped a lot of fluff for the TV series, and folded in quite a bit of the fifth novel.
The only thing I didn't really appreciate in the novel (but is ever so clear in the series) is how Holden is responsible for turning the planet on, and, as such, being responsible for ruining a whole lot of people's lives. I suppose that is his forte. He starts wars and causes shit-storms wherever he is/goes. He kills not just scores, but millions!
Alas-- the intricate plots and politics and mysteries built up in the first 3 seasons do grind down a bit (but they did in the novel too; moreso, in fact). It felt a little rushed in the last 2 episodes. I wouldn't have minded them stretching it into 10 episodes. But again-- they clearly knew what they were doing because they did make the source material BETTER.
They did over-Avasarala it up a bit, but damn she is such a great actress, so I didn't mind. I want to smoke 3 cartons a day just sound like her.
The Miller/Detective/bot was great to see again. I don't know if his ending (or even his mission) was completely understood if you didn't read the novel. I can't tell. But he's such a great character (although he seemed less tortured in Season 4).
Considering the source material, Amazon did awesome. Also-- it is beautiful to watch. The effects are stunning. The constant blueish tinge makes the actors/actresses look great.
Can't wait for season 5. But I also think it will be a lot harder to do. No spoilers. But I'm sure a lot of you know why.