Civilization V is currently on offer at a bargain price of £6.78
http://www.gamersgate.co.uk/DD-CIV5/sid-meiers-civilization-v
This is for the PC AND Mac version ( you get access to BOTH versions when you buy the game )
Installs using Steam ( who are selling it for £29.99 at the moment )
The game is a vast improvement on Civilization IV and very easy to play right from the outset. I particularly like the fact that the foreign diplomats speak in the correct language, with English subtitles.
I'd definitely recommend this game.
Also on sale at GamersGate is Two Worlds 2, which is currently £7.49
http://www.gamersgate.co.uk/DD-TW2/two-worlds-2
Deals end on Monday 29th I believe.