Sid Meier’s Civilization V: Game of the Year Edition is on sale at Amazon and GameStop for $12.49. GamersGate US also. £7.49 at GamersGate UK.
Also on sale for 75% off at Green Man Gaming but it’s only $12.48 there. So you could save a penny.
The game uses Steamworks, so it’ll require Steam activation no matter what.
BTW, if you want the regular edition it’s on sale for $7.49 at Amazon, GameStop, GMG, and GamersGate US. GamersGate UK has it for £4.99