You do not need Twilight Imperium. This game is entirely separate. It is a standalone as of now, though I very much hope for expansions down the line if it is half as good as it looks.
Yep, this is a reimagining of the old Dune game, the same game you heard about. Dune is a classic with a lot of interesting game mechanics:
1) The spice economy is pretty tight. You fight over random spice blows that appear on the surface of the planet each turn, and spend that spice to revive your lost troops faster, ship your troops to the planet (paying the Guild faction, now the Hacan), and purchase new combat cards (payable to the Emperor, or the Lazax faction). It seems that spice will now be called influence and may be gained in new ways, and perhaps used for other means, too. You can also bribe players with spice, one of my favorite parts of the game, at any time for any reason and even keep secret from others how much you gave or why.
2) The combat wheels. Each wheel has a dial of 0-20 which you use to secretly note how many troop tokens you're going to use in your battle. However many you use, that's your strength (plus your leader's value, also chosen secretly), but you also have to lose that many tokens whether you win or lose. The problem is, if you lose, you lose all your tokens anyway, so it's always a gamble. You can play weapons and defenses to try to kill and protect leaders, and in the beginning of the game you secretly obtain a traitor from among your opponent's leaders. If your traitor is revealed in combat against you, you win the battle automatically! Lots of intrigue and bluffing and second guessing makes each conflict rather nerve wracking.
3) Sometimes a giant sandworm would appear to devour all tokens at the previous spice blow unless the tokens belonged to the Fremen or their allies. It's unclear if there will be something similar in this game, but probably not. However, it was also at this time when you could forge alliances (for some reason... never really explained well thematically despite all the praise the theme gets), which is integral to both versions of the game, from what we've read so far. In an alliance you can use one facet of your ally's ability as printed in their faction text, and you could win together if you are still in an alliance when you've met victory conditions.
4) There is also a storm circling the board, destroying nearly everything in its path unless in protected areas. The Sol bombardment replaces this function in Rex.
That's the gist of it. There are a lot of optional rules for the game, and the bribery rule allows for all kinds of intrigue and upsets. Most love the game so dearly though because of how well it represents the theme. If you've read the original Dune novel, one read of the faction abilities and you will be eager to play as the Harkonnen and betray each of your friends turn by turn.
I personally appreciate the theme but love it mostly for the game mechanics, in which a lot of the strategy derives from the social aspect of the game (and seeing as you're a fan of the Game of Thrones board game, this may well appeal to you, too) rather than just going it alone the whole time and trying to play it like a no-frills war game. The game is from the makers of Cosmic Encounter and shares many little similarities while being overall more of a strategy game.