I see couple of you guys have this on your wishlist, do yourself a favor and play the demo. It gives you a good idea of what the game is about without being too restrictive.
The last time I binged on a game like this was probably when I played Factorio for the first time. 18 hours… 1 weekend 
This game somehow combines about 3 different genres without tripping over itself.
The ARPG gameplay is super satisfying with no shortage of physics objects being exploded, incinerated, shot and nuked across the screen. The number of on-screen enemies can get quite insane.
Enemies have resistances and weaknesses to certain damage types, so the constantly switching up of weapons and play-styles keeps it interesting.
There are weapon mods that drop from powerful enemies or alien nests; they not only increase your weapon’s stats, they can also modify the functionality. For example, add the homing function to a rocket launcher, you now have a homing rocket launcher.
The base-building is more reminiscent of They are Billions in that you defend your base and resources from intermittent swarm attacks. Much like TaB, you need to build up multiple layers of walls and fill every available gap with defensive towers.
The different biomes (essentially different maps) you traverse during a play-though offers different methods of producing power. I like this a lot, you can’t just plop down cookie cutter base designs. Some biomes offer 200% solar power, but increased risk of volcanic activity for example. Others are blanketed in thick, toxic atmosphere and you’ll have to refine toxic sludge into flammable gas to use in a gas power plant.
The gameplay loop involves building up your base, setting up mining operations, researching some things. New resources are required, so rift jump to a different biome, setup operations to mine the rare minerals, defend from attack. Jump back to HQ, research more. All the while fighting the never-ending alien swarms and growing your arsenal of sci-fi weapons. The goal of the campaign is to rift jump back to Earth which requires this monstrous and expensive to run, rift gate thing.
It’s a new release from a small studio (they made an action TD before this), so it’s not without bugs. In my 20 hours played so far I’ve soft-locked twice, hung on a loading screen once (since been patched) and had some other minor glitches, I feel like they know it’s still buggy since the autosave interval is 5 minutes by default 
Hasn’t taken away from my experience at all though.
At the moment there are 2 gameplay modes, Campaign and Survival, with talks of adding co-op multiplayer soon.
In conclusion, I’ve seen people describe the game as any combination of Factorio + dota + Starcraft + Diablo. I think a more accurate description is They are Billions (except in a sci-fi universe) with a little bit of Alien Shooter thrown in.
I’d give it a nice, biased 8.5/10, since I’m already partial to these types of games.