This is less a review than a public service announcement: I just finished the free DLC that was added to this several years ago now, and I found it significantly better than any individual chapter of the base game. It isn't a radical departure. If you found the base game's mechanics tedious, the same will be true of the DLC. Likewise if you found the base game's philosophy tiresome - this will not change your mind. But it features the best writing in the game and its story forces the characters to talk to each other in a way that characterizes them more strongly than before.

So, if you're at least mixed-positive on this and you haven't gone back to check out the DLC, it's worthwhile. (Maybe remind yourself of the base game's story first - it'll be a tough sit otherwise.)