I could have sworn I'd already done a post about this, but it seems not. I have to give a shout-out to
Discworld: Ankh Morpork - having got it for Christmas, I've already lost count of the number of games we've played in my house since then. It's very much a firm favourite.
(
I have to stress first off, you do not need to have read the books. Obviously you'll get a lot more from the game if you have, but the Discworld connection is window-dressing, really - the various characters could just as easily have been created for the game and it wouldn't change anything. Of the six or seven people I've played with, only two have read any of the books, but everyone loves the game.)

You play as one of seven possible different factions vying for control of the city. It's all about gaining control of city areas, collecting revenues, constructing buildings and infiltrating your minions as far throughout the city as possible, while muscling out (or assasinating) the opposition. Like all the best games the actual turns are very simple - from a hand of five cards, you pick one to play, and do what it says on it. Then draw back up to five cards. The only thing that initially takes a bit of time is learning the symbols on the cards (may take you a few games) - nothing else is particularly complicated.
The genius comes from the fact that your victory aims are different every time, depending on who you pick to play as. One of the characters is trying to collect a certain amount of money; another is trying to run down the card deck; one needs to gain majority control of a certain number of areas; one simply needs to cause as much chaos as possible. So as well as trying to achieve this, you're also trying to guess who the other players are and throw a spanner in their plans if possible. It also means you're never quite sure when the game's going to end, as you're never sure how close everyone is to achieving their aims. I now know the game so well that I have great fun subtly pretending to play as another character to draw the attention away from what I'm
really trying to do.
It's really well paced, too - the latter cards begin to allow for more assassinations and sabotage, and there's a huge increase in the number of random events (can be anything from earthquakes, fires, demon infestations, riots or dragon attacks). So the longer the games lasts, the crazier and more chaotic it gets. And it looks absolutely beautiful - the cards, the board and even the box are really well designed.