Questions about m effect 2?

I havent had a chance to play m effect 2 yet, ive beaten the first one though, but i just had some quick questions about the story of ME2. In ME1 i loved the story of the mysterious culture of the protheans and the inscrutable reapers, it kept me at the edge of my seat. What is the story in m effect 2? Does the story of the protheans carry on in ME2? I know the reapers are in #2, the reaper Harbinger instead of Sovereign. What is the story of m effect 2?