Summary: I was a big fan of the original Enemy Unknown, and am glad they went back to this style of gaming after the flop of "The Bureau" which was ok-ish but not nearly as absorbing or entertaining in my view. This is a stand alone expansion of the original Enemy Unknown, and somewhat disappointingly is EXACTLY the same story line, with almost all the missions of the original repeated.
Summary: XCOM Enemy Within is the follow-up expansion to the hit revival of the XCOM franchise, Firaxis's 2012 XCOM: Enemy Unknown. It brings new enemy types, new factions, new weapons, Mech troopers, genetic modification, and a whole host of other additions. The good: More maps added to the pools for all types of mission, although perhaps not quite as many as I would have hoped for.