It's a great game. It's more about the gameplay than the story, although it has a better story than most of those kinds of games I felt, and it has instanced sort of smallish areas where you fight monsters and/or a boss (archfiend). Every story mission and quest is in these instanced areas.
The coop MP is where the game stands out, and you have to complete the first little story chapter of the game before it unlocks the MP for you to play. It has a bit of a learning curve but it's a lot of fun when you get the hang of it, I spent like 70ish hours on it and they gave out some free dlc (one that had an additional 8 quests even though 2 of them were kind of minor) and are giving a few more free dlc packs in the coming weeks.