Theres a very vague main storyline that has you finding the overseer of the vault you just left. You find notes and stuff that guide you through it but there are no NPCs to interact with or anything. It's mostly just loads of side quests that you do with your friends to be honest. You can work together to get a nuke though and thats sort of another quest. It's an interesting and completely different concept from previous fallout games, great for the short term but like I said, not sure how i'll feel in a few months.