If you haven't played Xcom: Enemy unknown well that the time to try this version. they added a lot of new maps that make the game less repetitive. The new resources to do the new research push you to act differently on the field. Some part need to be taken before they get lock. New enemy's force you to stay together so your strategy change a lot since enemy's unknown. I bought this game because i think it was a simple add on so i can continue my mission but the game restart form the beginning. you need to research everything you did before on enemy's unknown but its not boring at all because all the new research force you to make new decision on what will be your next research and where you going to spend your money.
If you like strategies game well that really a good one to try. the game can be set as usual easy normal and hardcore gamer but they added few feature like random damage, random customization of a character if you don't like to spend some time to do it your self. The one i prefer are for the save game feature, every time you load the save game enemy character can act differently even you did the same move. so you can save and reload to do your perfect attack
I recommend this game even you bought enemy unknown because this is more rich and the game look more finish than the other one and trust me the new feature are really fun to play.