This game is essentially a version of Dungeons and Dragons (or similar), in which you explore a world corrupted by chaos, fighting monsters and completing quests. You play as fighters or wizards, hefting enormous weapons or spells, while rolling skill checks and trying not to die. Which you'll probably do a lot. This game has a level system. Don't aim too high.
I'll admit, I've only played the local co-op mode thus far, as I've been looking for a game for the Girl and I to play together. This seems like a good one. We have spent quite a lot of hours shouting at the game, each other, tiny monsters and the cafetiere. (Late night play sessions need coffee at our age.)
It's turn based, with each player/character going indi\vidually. The fight system is similar to anyone who's ever played a JRPG, but has a reasonable element of randomness. Even after a few hours play, I don't think I've quite got the nuances of how it works, so possibly some googling required.
That learning of the system is part of the fun though, as you have some enjoyable "oh, that's how you do it" moments as you progress further through the game. I'm assuming that completing it is possible, it's just going to require a bit of a time input.