Potential spoilers
A couple hundred pages in, the pacing just felt too slow. The "high stakes" that kept me on the edge of my chair felt like they disappeared. Where I stopped reading, Mars was collapsing, Earth had collapsed (something that might be fixed in many generations), and the Belt was divided with Marco facing mutiny. And the Marco character went from seemingly having some grand plan and being 10 steps ahead to seemingly being just a charismatic thug who got lucky. Who really built the Protomolecule? In Holden's vision, who were the people who killed the people that built the Protomolecule? Where did they all go? Are any of those civilizations still alive? The first three seasons of the show and even books had a political/human struggle angle, but the Protomolecule and the alien tech were the glue that kept the story progressing. Even in Book 4 with New Terra from one of the ring gates. But seriously – Book 6 – the pacing of the story just turned me off. They could tell me in one chapter that Inaros and his crew got blown up and we don't have to talk about them anymore, and I wouldn't even be mad.
I know there are more books. At some point between now and when the next season of the Expanse airs on Prime Video, I'll probably finish Book 6 and move on to the remaining books. But seriously – Book 6 has hurt my brain. And I'm sad to learn that it'll be the final season of the show.