You can get right into it with the Third man, it doesn't really tie into the other two, so you wouldn't be lost. It really is a great game, co-op is fun, and playing alone is still a lot of fun. There's tons to do in this game too.
Please let old threads die and do not reply to them unless you feel you have something new and valuable to contribute that absolutely must be added to make the discussion complete.
Otherwise, please post a new thread in this forum instead.