http://xbox360.ign.com/articles/787/787584p2.html
"IGN: In terms of novel-lengths, how many pages or books worth of writing would you estimate you've done for Mass Effect?
Drew Karpyshyn: Mass Effect has a word count of around 400,000 words - somewhere in the area of 4-5 full novels. But, unlike a novel, we also have visual images and other ways to tell a story. Our word count would be even higher if we had to describe settings or characters, but we actually have art and graphics to do that for us. I think a better comparison to give the full scope of our game is to use movie scripts. In Mass Effect, every line of dialog has full voice over, and we have 20,000+ lines of dialog - roughly the equivalent of 20 movies. That seems like a lot - and it is - but it's necessary to keep a player engaged in our game and story for the 20+ hour critical path."
"IGN: In terms of novel-lengths, how many pages or books worth of writing would you estimate you've done for Mass Effect?
Drew Karpyshyn: Mass Effect has a word count of around 400,000 words - somewhere in the area of 4-5 full novels. But, unlike a novel, we also have visual images and other ways to tell a story. Our word count would be even higher if we had to describe settings or characters, but we actually have art and graphics to do that for us. I think a better comparison to give the full scope of our game is to use movie scripts. In Mass Effect, every line of dialog has full voice over, and we have 20,000+ lines of dialog - roughly the equivalent of 20 movies. That seems like a lot - and it is - but it's necessary to keep a player engaged in our game and story for the 20+ hour critical path."
