I have honestly never been happier with spending £15 on a game, why? because I'm on it literally every single day without fail as I have become addicted since I bought it 2 years ago. If you love zombies then there's no question about it, you need this game. There are four characters that you can choose from; Ellis, Nick, Rochelle and Coach - all of which have their own background and personality. You are a first person shooter accompanied by the rest of the characters as your fellow team mates that will help you fight hordes of zombies and "special infected".
Special infected are extreme mutations of zombies that will go out of their way to end your life, literally. Unlike the first Left 4 Dead, you now have a new range of guns and also have melee weapons available which comes in handy! There are a number of new features and some new zombies. You also get the opportunity to play as the special infected on the "versus" mode on xbox live multi-player, along with scavenge (trying to collect 'gas cans' and fill generators before all the zombies get you) survival - seeing how long you can survive before you're all done for and campaign - both solo and on-line with other players providing you have a xbox live gold subscription.

A handy tip for new beginners, always play through the campaigns 'offline' before you join with other people on multiplayer, just so you know how to play the game and enjoy the experience more.

If you're unsure, there are demos available on the xbox live market place, just search the name and you'll be able to download one of the chapters from "the parish" level and experience off or on-line play.
I look forward to finding more of you on there!