In it's current state, you can play through the game.. but not save it. In it's final state, the game will automatically save every so often or after an important event, then load upon start-up. You won't be able to load previous saved games, so that everything you do in the game world will be persistent and permanent.
I've just begun on this. This isn't my first attempt: I'm using WhyDoIDoIt's save asset and integrating it into my game. The only difference this time around is that I've figured out that there was a bug (since-fixed) preventing it from working the first time.
So far: I have the included menu-driven system working completely. My first goal is to make sure that saves and loads work correctly. Right now, they don't. Doors will load in their correct state, but will not work after loading. Text is jumbled, because I'm not saving the material yet, and I haven't even begun on saving the enemies yet.
But! Most things DO save and load correctly, and all the issues are mostly just cosmetic, so that's an excellent start! After I do have saving and loading working perfectly, I'll be able to tackle the issue of saving in the background without introducing too much stutter and loading the game on start-up.