"The Expanse" takes a lot of its cues from ASOIAF. Not only is there a POV-chapter structure, with the individual chapters bearing the as titles the names of the main characters whose POV they're representing. The story also uses a casual violence that's akin to the random death permeating Westeros, creating a "serious" setting in the process. Politics play an important role, and they are largely a deadly destraction from the true danger humanity is facing. There are a lot of difficult decisions to make in morally grey areas, with few people really innocent or irredeemable.
The novels and the show both shine in their really strong sense of setting. The Solar System of "The Expanse" is a vibrant place, feeling real and interesting in ways Westeros never managed for me (which feels real enough but isn't all that interesting without the characters in it).
While the story itself is hugely enjoyable, there are shortcomings in "The Expanse" that are interesting to look at in the light of its obvious model, the ASOIAF novels.
There's the POV structure, for one. It's the core of what makes ASOIAF special and makes it work on the grand level that it does. However, just using them as cameras doesn't in and of itself much, and where "The Expanse" fails is to make these perspectives interesting. While reading the novels, I repeatedly though that having an auctorial narrator might just work as well as the personal narrators the novels were using, because they simply weren't really different. You get a new appreciation for what Martin is able to do when you see how little individuality the voices of "The Expanse" are bringing to the table. Everyone cusses, to the point of numbing the audience, everyone uses the same catchphrases (starting a sentence with "Look..." is the most egregious offender, EVERY character does it to some degree) and their style of talking isn't different at all. So why have POV chapters? It's almost a cargo-cult going on.
The same is true for the dialogue itself. It's incredibly clunky at times, with sentences that don't sound natural at all, but rather like prose. Again, that is nothing that you can find in ASOIAF.
"The Expanse" also has the tendency to spell out all of its themes explicitly, mostly by the characters' interior monologues. Where in ASOIAF, you have to read between the lines, when a character in "The Expanse" is a religious fanatic reading a situation wrong, it will be there on the page in an explicit manner, pointed out by the POV character.
The themes are also a bit muddled. While it is clear that the conflict between Earth and Mars is a frivolity that binds resources that could be used to better effect elsewhere, and the same applies for the Belt, other things are less clear. This is especially true of violence and the role and legitimacy it has in solving conflict.
The last thing where "The Expanse" falls woefully short is in its gender politics. It's the men who have to make the hard decisions, while the women act as their moral consciousnesses, relegated to the sidelines. For the 24th century, the gender politics of the Solar System are stuck in something like the Mid-Aughts. It's not a pretty sight.
It's also weird that while the characters start each novel in wildly different places, they are drawn to each other as if by magnets (or, in this case, the author's fiat). If you compare this to the frustrating missing of characters and time it takes especially in the Feastdance, you get a new appreciation for what Martin is doing, because the inevitability of all the characters ending up at the same place (and often the same side) takes away a lot of excitement and robs you of the major advantage of ASOIAF's POV structure, which is showing the same dilemma from different sides.
Generally, "The Expanse"'s shortcomings show you just how good a writer George R. R. Martin actually is, and what hugely important role taking your time and rewriting such things plays. The next time you are angry at Martin for taking so long, consider that the alternative, while being an enjoyable read of its own, does not reach the heights of art. That's the price that needs to be paid.