We picked this app up when it was a free download, but even so, $8.99 is a small price to pay for the brilliant time vacuum that is Civilization Revolution.
Essentially, this is a finger-friendly version of the classic Civilization games You develop your civilisation from the dawn of time to the future, advancing them through either military, cultural, economic or scientific means. You can choose from any of 16 different civilisations throughout history across the globe with each leader bringing certain benefits to your campaign.
As a turn based game, Civilization Revolution takes a long time to play, no matter what difficulty setting you use. But considering just how addictive it is to wipe the floor with your enemies blood, that doesn't matter. You can also save your game as often as you like, or thanks to multitasking now on the iPhone, you can just leave the app running in the background to pick up and play whenever you have a spare hour.
At the moment, there's no Game Center support, which is disappointing, because the thing that would really make this game as good as the PC version would be the ability to play friends online. Considering it's turn based, it shouldn't be too hard to implement either. Here's hoping 2K are working on that feature right now.