The original series is something you have to play You don't and probably shouldn't pick up mass effect 1 since it had very bad gameplay but still a great story the reason why is Mass effect 2 comes with a free downloadable comic strip which after starting the game runs down what happened in the last one. Mass effect is about the exploration and defending of the Milky Way against the reapers a sentient machine race that wipes out all organic life in the galaxy every few hundred or thousand years