Basically a sci-fi Total War game. You have the campaign map where you buy ships, order fleets onto missions, and generally have a nice 4X time. When you encounter another player -> zoom into the tactical map for real time action.
The campaign map is beautiful, each faction gets a different movement mechanic from the standard warp drive of one race to instatanious gates and node lines of others. You really feel like a unique race not a re-skin. This keeps up with the ship designs, some races are hulking great beasts, slow and powerful, others are quick and fragile. Humans for instance have decent all-rounder ships, slightly less well armed than average but fast over the strategic map, unfortunately the drive section is very fragile and can strand your ships far from home.
Did I mention that? Yeah your ships are distructable in nice modular chunks, from individual turrets to command/mission/drive sections. Add to that a 4-facing armour matrix, shields that are very well balanced IMO, weapons that all have a use (though you will rely on a few favourites if you don't have a special need), and the tactical combat will keep you entertained alone.
It's shonky, no two ways about it. The campaign UI is a bit slow to respond, after about 200 turns it takes quite a while for the calculations to play out and ocationally crashes (but that has got much better since release, in fact no crashes for ~ 3 months). Sometimes stuff doesn't update or doesn't work for no particular reason, and last but not least: THERE IS NO IN GAME WAY TO LEARN.
Yes that annoys me, you spend countless man-hours making a great combat game with a slightly shonky campaign layer and don't tell anyone how to use it. Thankfully the community has stepped up to the challenge and fixed this, creating beginners guides and guides on individual races (start with the Tarka, they are the most straight forward - or Hiver if you like to turtle). The guides are good, use them.
Another area that needs attention is the AI, it's pretty bonkers. It will declare war on your massive empire and send colony ships to bombard your planets which get killed straight away by planetary missiles (did I mention missiles, yeah there are missiles, and point defence for your ships, and weapons platforms... I like the tech). It will also be bestest mates with you but be mildly miffed you "stole that tasty planet near me" for 100 turns and then declare a holy war to wipe the stain of your civilization from the galaxy with 10 Leviathan class ships when all you wanted to do was trade with everyone and be a mecantile hippy empire (still sore about that).
When the campaign AI works it can be pretty impressive, I think it managed to plan an invasion once and pulled it off simultaniously against me and two other AI. That invasion was let down by the tactical AI (better but not exactly Sun Tzu) and a wall of torpedo platforms.
Three words, randomised tech tree. Some people hate it, some love it. I am in the second camp. But, I also loved the randomised discovery in Alpha Centuari (I don't care if it's not balanced, that's how science works guys, sometimes you miss a really obvious idea). Certain techs are always available, like cutting lasers, and dreadnought ships. Others, well, it's the luck of the draw. The Zuul are having an energy weapon bonanza and enslaving your planets? If you're lucky just research the "♥♥♥♥ you energy weapons" shield (only covers the front, not quite as OP as at first sight). If you're not lucky, well hopefully the cash you save in equipping that shield will let you build more ships and the Zuul run out of light to put in their lasers. It's about rolling with the punches, but it is pretty galling when those punches are a fleet of heavy phaser drones and your stuck with the crappiest point defence. It's also pretty horrible when your home planet gets glassed 10 turns in by a ghost ship.
Yeah, ghost ship I hate the ghost ship. Like a '90s RPG you are subjected to random encounters (I think they are not completely random but it feels like it). This mechanic is at the same time absolutely horrible and absolutely brilliant. It's horrible when 10 turns in, your economy is trashed by a giant wandering ♥♥♥♥♥♥♥ (built by the humans and then lost forever to wander the stars... the lore is actually pretty cool). It's brilliant when your struggling colony, with only that admiral you should retire because he got the shakes (yeah your admirals have stats, some are mass murdering ♥♥♥♥♥♥♥s, some just like to grow flowers) - but can't quite let go because he won that battle that one time - and a couple of second rate ships for support, is being slowly worn down by slaver attacks. Admiral shaky holds his battered squadron together while the new guy from the academy is bringing reenforcements in the form of the newest (and cheapest) system defence craft.
The random encounters make you feel like starfleet command, an ancient derelict in one system, a hive of wasp-like silicon lifeforms in another, colony alpha-nine has an incoming metor shower. More variety would make it perfect, an option to turn off mr ♥♥♥♥♥♥♥ ghost ship would be sublime.
Would I recommend this? Yes I would. Mostly because it deserves to do well. It improves on everything SOTS1 fell down on and expanded what it did well. It's not perfect by any means but it has ambition that alot of sequels lack. Paradox could have played it safe, they could have updated SOTS1, make a few fixes to the dodgy bits and called it a day. They didn't. They fixed the broken stuff and then said "You know what would be cool? Building science stations to observe pre-FTL aliens. Letting players build Bablyon 5. Treaties that real civilisations would make (re-create the treaty of Farixen). A ship that shoots asteroids at planets (actually in the first one but it's really cool)". Like I said some of it doesn't work, the science stations are better suited to sitting behind your lines researching important things, from what I can tell Bablyon 5 doesn't do much, the AI won't make interesting limitation treaties with me, but the asteroid gun is great.
The tactical combat is the best bit, the strategic map feels like a way to move ships to make fun battles happen. I really wish Paradox would release a single player campaign about a lost human exploration fleet, a load of linked missions with persistent officers who learned? Excellent. In the mean time, admiral shaky has some slavers to kill.