IGN does a good job within there 3 minutes. Didn't really miss anything important, I still got it whilst playing AC 2/Brotherhood. Still need to play Revelations though, just a bit poor atm.
The ending of Bortherhood was epic and for the entire year I was thinking all kinds of things (about the event that occurred) and now can't wait to play Brotherhood, but Revelation won't make sense at all without playing Brotherhood or unless you get a friend to tell you whats going on or watch videos on youtube.