A spiritual sequel to Starcom Nexus by the same developer, it's a basic ARPG heavily focused on exploring a semi-randomly generated universe.
The basic game loop is to enter a new system and fight off any hostiles, then scan the planets for anomalies and send down away teams. Away team surveys play out in short text adventures and reward you with research points and materials. Back at your home base you use research points to unlock and enhance ship components from a research tree that wouldn't look out of place in a space 4X game. Then you use materials to build new ship systems and rebuild your ship hex-by-hex. At which point you sally forth in your improved ship to do more fighting and exploring.
Exploration is what this game is all about. Don't come expecting space combat of StarSector's complexity, it's closer to Star Control 2 in gameplay, albeit with everything happening on a single continuous map that you can explore in any direction, though the game gently nudges you along in a certain direction with its collection of fast travel flingers and wormhole gates.
Compared to Nexus, this game gets you straight into the action faster, albeit at the cost of losing some of the original's atmosphere of your ship and the station being lost in the middle of nowhere. Besides the graphics being prettier and the ship design more interesting, Unknown Space adds a smart autopilot that lets you Ctrl-click any object on the map screen and your ship will go there at best speed, making use of all fast-travel options to speed up the trip.
These are still my first impressions but so far I'm delighted!