I sunk a lot of time into this when it first came out and still enjoy the odd wee bash at it. Its a slow burning strategy game set in the middle ages which has a real 'one more day/turn' factor to it. Starting as a young entrepreneur with a single low grade business to run you must build your character - and their dynasty - into the leading family in their city. You do this by expanding your business as well as by engaging in local politics, diplomacy, terrorism, poison, religion and witchcraft.
I particulary like the way you can play at your own pace and difficulty levels are extremely scaleable. You can micro manage at your leisure and then zoom time on to see the effect of your actions and, while its easy to make mistakes, you usually know that when you suffer a setback it is because of your own ineptitude rather than a random dice roll somewhere in the depths of your PC.
I originally played the vanilla game which made a bit more sense and was more realism based as some of the expansion pack additions are quite freaky. As a long term player I welcome them but would recommend newer players start with a mundane business for their first few games.
Not one for the FPS brigade but I would highly recommend it. It was never a graphical delight but gameplay has aged well and I still far prefer this one to its sequel.