[Alert: Minor spoilers for James S.A. Corey's "Expanse" book series, and presumably the show as well.]
When you're trying to get someone interested in a new series of books or TV shows, it's natural to try to compare it to something they already know. When Breaking Bad was new, it was often compared with Weeds, though the two shows have nothing in common besides a regular person who starts dealing drugs. When I tried to get people to watch Sons of Anarchy, I often called it "The Sopranos with motorcycle gangs," though again the connection was tenuous except for the fact that they're both based on organized crime.
So it is natural that even before SyFy began adapting James S.A. Corey's The Expanse series, beginning with Leviathan Wakes, people trying to convey the scope and power of the series compared it to the best-known non-YA speculative fiction series out there, The Song of Ice and Fire series, known on TV as Game of Thrones. From a distance, they seem very similar. You have a long series of doorstopper books. You have brutal and underhanded struggles between competing powers in a sprawling world, or in the case of TE, solar system. You have violent battles, different points of view, and even a kind of zombies in a particular scene on Ceres. But though these are both engaging and powerful series of books (and TE is now a TV series as well), TE is at its core nothing like SOIAF. And that, I argue, is a good thing.
So how are the different? Here are a few ways:
The main reason that the SOIAF series was such a significant was that it has no real heroes and no happy endings. The two characters that are closest to being heroes in SOIAF are Tyrion and Daenerys. They are both engaging and wonderful characters, and morally they are better people than most of the other characters we encounter on Westeros. But that's a pretty low bar, and they're both pretty morally flawed. Most of the other characters SOIAF set up as heroes, especially when it looks like they are winning, have a Red Wedding-level event to look forward to.
This is a good thing, I would argue, because unlike SOIAF, TE is showing us a vision of something that could actually happen (up to the point they start encountering alien artifacts, at least). This is distinct from most science fiction we've ever seen before as well, which usually feature teleporters or warp drives or other technology we're unlikely to develop in the next few hundred years. This means this series has the potential to inspire space exploration in a way sci-fi has not in a very long time. But to do that, it needs to make us believe that the future we're working towards isn't just a Machiavellian hell.
2) Far fewer and more traditional point of view characters
Another way that SOIAF was distinct was the enormous number of POV characters. GRRM is a master storyteller and was mostly able to make this work (though it gets a little out of hand later in the series, if you ask me). I have encountered too many authors lately that have tried to emulate GRRM in this way, too often resulting in too many interchangeable people I have no connection to or interest in. Because GRRM was able to succeed at this, we found ourselves having interest in the stories of otherwise pretty unsympathetic people, like Jamie Lannister, who tries to murder a child in an early part of the first book.
Though TE has multiple POVs, they are mostly pretty focused on the heroes of the book. The main POVs of Leviathan Wakes are the Rocinante's crew and Detective Miller, all of whom are soon revealed to be tracking down the same mystery. The TV show introduces Chrisjen Avasarala in the first episode, though in the book series that character doesn't even appear until Caliban's War, the second book in the series. I suspect the showrunners introduced the somewhat Machiavellian Avasarala at least partially to add a little more Game of Thrones-y morality to the show, as can be seen by the way she's engaging in the torture of an OPA spy in the first episode. But the direction of the book series is going to make it necessary to focus more and more on the adventures of the Rocinante's crew as the books do, especially starting from Caliban's War.
This is good because, first of all, SOIAF's sprawling cast of POVs is almost impossible to do well, and second, now that it has been, really doesn't particularly need to be again.
The GOT series on HBO often gets called out on its "sexposition," excessive nudity, and unnecessary rapiness. But let's be clear, this level of creepy sex is not a departure from the books. Yes, there were a few rapes in GOT that weren't in SOIAF, but believe me, there were a lot more that were in SOIAF that GOT left out. Mostly SOIAF and GOT both portray a world full of sexual exploitation and unhealthy sexual relationships. It says something when one of the healthier sexual relationships in your books is between a brother and sister (though it's not so healthy in the show).
Though it's clear that there is prostitution and probably exploitation happening in some of TE's space stations like Ceres, this is never really central to the plot. The main sexual relationship that occurs in TE is the one that develops between Holden and Naomi, which, though it has its bumps, is pretty normal.
Do I need to explain why this is good? Hopefully not.
The main difference between The Expanse series, both in the books and hopefully on TV, is that unlike SOIAF and GOT, they are guardedly optimistic. And since these are portraying a future that is at least partially available for us, we really need that.