For a game still in beta, Galactic Civilizations III is already a solid 4X game. But it still has bugs, and the campaign is also not available yet, so if you want to play a complete game, wait until the release. But if you are dying for a science fiction strategy game and can live with the bugs, then go get it. And it will continue getting better, even after the release.
You can design your own ships, and not only regarding its weapons and components: you can completely change their look, add blocks and parts to create your own aesthetics and etc. You can make your own unique custom civilizations, give them special traits, characteristics and ships. The visuals are awesome. The game will be fully modable, that is, modders will be able to create incredible things. The battles look epic, but beware that you can't play them, as they are meant to be looked at and see the efficiency of your ships against the enemies. The AI will be getting better and better as the release approaches. There are several events with choices for the player to make, but so far, there are no "massive" events that change gameplay or add new factions, which I would like a lot to be added. Also, the devs are awesome and listen to their fans.
The game series has a very interesting story, which you can take a look at here (http://www.galciv3.com/databanks/timeline)
and here (http://www.galciv3.com/databanks/our-story).
But even if you aren't interested in the story, you can always play a normal game outside of the yet to come campaign and create your own backstory.
One of the things I feel that is lacking in the game though is a deeper soul. It need politics, bigger events (like I mentioned above) and more things to illustrate the universe and your civilization. But the devs do have plans to include LOTS of interesting things in the expansions to come... so I have hope for these features.