Civilization 5 is free to play this weekend and the entire Civ5 franchise is 75% off. I suggest trying it out during the weekend, and if you decide to buy it, I highly suggest buying the Game of the Year edition for $12.50 (includes all DLCs, the map DLCs are useless but the extra civilization DLCs are very nice). The expansion Gods & Kings, which will add Religion, Espionage, and tons of more new neat things, comes out June 19th for $30 I think. So buying this now on sale will save you a boatload.
