There's a scene in the beginning of Mass Effect 2 when a Cerberus operative walks into the room and shoots someone in the head without missing a beat. It's about as dramatic as an entrance can get, but it sets the tone for the game beautifully. Mass Effect 2 grabs your attention with its jaw-dropping intro and refuses to let go, dropping you directly in the line of fire. Want to save the universe? Hope you're ready to get your hands dirty. There's no such thing as good guys or bad guys anymore, just the ones who live and the ones who don't.
Normally, I'd begin my review by giving you a brief overview of the game's plot, but I'm not going to do that here. The story of Mass Effect 2 is, I think, best experienced completely fresh, and I don't want to ruin it by telling you too much about what to expect. I will say that once again, you're in command of the Normandy, and you need to assemble a team of specialists to help you on a mission to save humanity. Things have changed since you last saw Shepard; new crew members take the place of old friends, and the universe isn't quite how you left it. Hard days lie ahead of you and your team.
You don't need to have played the first Mass Effect in order to pick up the second, but you're probably going to have a better experience if you have. Mass Effect 2 does its best to catch you up on the major events of its predecessor, but there are many small references sprinkled throughout your adventures that will be meaningless if you're coming in brand news. You can also carry your character from a completed game over into the new Mass Effect, in an extremely easy process that sets you up with varying bonuses depending on your Shepard's level. You're also given the option to change your saved character's appearance and class if you want to branch out and try something new.
Conversation and relationship building, a major component of Mass Effect is an even more important part of the sequel. Your team members unlock new abilities once their Loyalty is high enough, so taking the time to chat them up isn't just entertaining busywork. The innovative dialogue system, which made conversation feel more organic and less like choosing from a menu, remains intact but comes with an intriguing upgrade. At certain key points, an icon will flash on screen allowing you to select a Paragon or Renegade action, such as offering medicine to a plague sufferer or letting him die. These opportunities only last a moment before they're gone, so you'll have to pay attention during conversations if you hope to catch them. It's not terribly frequent, but it does create an undercurrent of spontaneity that doesn't normally exist in videogame conversation.