Another option , if you can read faster than you can play/beat games , is read the second halo novel Halo : The Flood , which summerizes the story of the first game while also filling in gaps of what happened between the gameplay levels. I thought it was a good read , as was the first and third novels as well.
Not much you can do about the second game besides play it , read a wiki summary , or watch the cutscenes at bungies site.