AFAIK they're all standalone as they are all different campaigns. If you buy the original Guild Wars you'll notice upon your first play through you have a choice of campaigns, the original compaign and a shadowedout factions campaign. I'd get Guild Wars special edition if you can find it as it's £10 in most places, ie Game and Play.com. I got my special edition from play.com, but im not sure if they are still selling it. Plus that way you can see if you like the game and whether or not to buy the extra campaigns. Plus you can buy the extra campaigns from within the game as well.