Yesterday, 2K Games and Valve touted the fact that Civilization 5 would take advantage of many of Steamworks' features, including achievements, and easier access to DLC and matchmaking. What was not made implicitly clear, and what GamePro was able to confirm via a 2K representative, is that the game will require an installation of Steam for all customers, including those who purchase the title at retail.
Steam is hoping to make the downloadable version a much more attractive option, as the announcement also includes news of the Civilization V Digital Deluxe Edition, which includes an extra civilization, a video feature, and the game's soundtrack. Additionally, customers who reserve the either the standard or Digital Deluxe Edition will receive a free map pack for the game. In the meantime, Steam is running a 75% off sale on all versions of Civilization III and IV. For more information about the Civilization V Steam extras, click on the source link below.
SOURCE: Sid Meier's Civilization V Shipping with Steamworks [Steam News]