I've been playing Left 4 Dead for several months now and can easily say it is one of the best FPS games i have ever played, It is so well designed and melds so well that it creates a fantastic single and multiplayer experience.
I am a big fan of stories in games and the great thing about Valve stories has not been the stories themselves but Valves unique way of presenting them and this is continued in Left 4 Dead with the saferooms in between levels littered with messages written on the walls but lets take a step back, for those who don't know in Left 4 Dead you play as one of four survivors in the zombie apocalypse.
The game take you through 4 campaigns each with a seperate theme, players will combat hordes of standard infected as well as special boss infected using the tools at their disposal which range from Pistols to Pipe-bombs to petrol tanks.
The game standard campaign mode can be played in either single or multiplayer but the game also features a unique versus mode in which one team of players plays through the campaign as the survivors and another team plays as the boss infected trying to stop them.
The game however excellent it is, does have shortcoming such as a the 2 missing campaigns for versus mode and a lack of online stats similar to COD4 or Halo 3.
But overall i would Highly Recommend Left 4 Dead as it is Valves latest Masterpiece for the FPS genre.