The "Green Flu" has infected most of Pennsylvania, leaving the general population as a bunch of extremely aggressive mutants. A small but fierce group of 4 survivors find themselves in the middle of it, and they want to escape. They may be lucky to be immune, but they aren't going to escape easily.

I hate infected! So do these four immune protagonists, and they aren't reserved about killing as many as they can aim a gun or throw a grenade at. I started playing this game because of the co-op part of it, and loved it. Jumping into a survivors shoes along with a few friends and rampaging through a few chapters never seems to get monotonous, but on to a more serious perspective. While the multiplayer may be the highlight of this game it's surely not the only good thing you'll find. The chapters, while limited, are well designed, take just about the right amount of time to complete, and have enough independence to let you play whichever one you want without feeling like you missed something. There's also the ever-watching AI "Director" dictating what you will face and commanding special infected against you. Here, I'll elaborate(If you care about spoilers in this game then warning):

1. "No Mercy" - Oh yes, I like this chapter. The idea in this one is to cross a section of the city, from where the survivors have regrouped to Mercy Hospital. An airlift from the roof is their hope of escape. It has a good balance of environments; from city streets, subways and sewers, to inside the hospital itself. The crescendo event on the roof of the hospital is my favorite in the game.
2. "Crash Course" - The helicopter that was rescuing them from the previous chapter has crashed in an industrial district. It's one of the more eerie chapters in the game, I guess it's just the dark streets and looming industrial structures that make it seem so un-homely. The Survivors escape at the end via an armored delivery van, the crescendo event is one of the more uncomfortable ones since you have to keep a generator running while fending off the hordes.
3. "Death Toll" - The survivors reach an impassable road-block, so it's back to walking in this chapter. There's a well done event at a church, some residential areas that are nicer than most places you go, and a bit of walking around out of town, which is dark and creepy, and unavoidable. The survivors escape via a fishing boat at the river, I always found myself unusually relieved to escape this chapter.
4. "Dead Air" - The survivors get dropped off on the other side of the river. With the objective of the International Airport this time, they push through a business district, some residential apartments, and eventually what's left of the airport to make their escape. A nice mix of not so scary areas for people like me. I'd have to say the crescendo event at the end of this chapter is the easiest one, with an almost casual feel in the exceptionally large open defending area.
5. "Blood Harvest" - With the Survivor's luck remaining consistent the plane promptly crashes on the edge of a National Forest. This mission involves walking through forest areas which are very inhospitable, along some isolated train lines, and through some tall fields of corn which hides oncoming infected. It concludes at an old farm house where the survivors are rescued by the military. All up a very dark and miserable chapter.
6. "The Sacrifice" - I haven't actually played this recently released chapter, but the idea behind it is something like this: The military base where they have ended up gets overrun by infected, forced to flee again they make an attempt to reach the supposedly uninfected Island of Florida Keys. During the chapter, the survivor Bill sacrifices himself to allow the others to escape to safety. This also connects with a Left 4 Dead 2 Chapter, called "The Passing", where in Left 4 Dead 2 the two surviving groups meet. No reviewing for this chapter, but it's nice to see Valve care enough to release another map.

All the maps in Left 4 Dead are based on four main sections of play. These are separated by "Safe Houses", where there are weapons and medpacks and all that good stuff. It's a really clever way to do it, it helps break up the game and gives players a chance to grab a break. Each chapter can take between 25 -75 minutes depending on level of difficulty and skill. There are also unofficial maps that can be downloaded from varied sources, I'd recommend trying them if you've played this game a lot and wish you had something different. Besides the co-op there's also the option for single-player, which I personally never did, but it's nice to have it(for those braver than me). In co-op with less than four players the remaining survivors are controlled by AI, which are sometimes a bit retarded but otherwise well balanced. They kill enough infected for you to notice, and are most useful with special infected, but you couldn't rely on them. The characters are likable and memorable, each with well-played personalities. They should be commended for not giving up with the amount of bad luck they have. The interaction with voice commands is pretty well done, there's an array of voice plays you can use at the touch of a button, and you can even bind many more sound files to any key by using console commands(which has proven to be fun). Besides that there is an 8 player vs mode in which one team plays as infected. This is actually pretty exciting. The game gives you a large area of map in which to try to stop the survivor(s) from reaching the safe house. I always failed miserably at this, but that's just me.

This game is definitely one of the top co-op experiences out there. There's lots of unique elements you don't find in other games, and it deserves all the reputation that it has. That's it for my review, thanks for reading and hope you enjoyed!