So here's the thing:
When it comes right down to it, I think there's two major approaches to writing something big based off existing material. There's "writing for plot," and "writing for characters." (In which the plot serves as little more than a vehicle to get us from one important character-exposition moment to the next.) For the most part, I think the really huge projects, the novel-length stuff tends to mostly fall into the "writing for plot" department. And I actually think that on the whole, we've exhausted this area. It's been ten years since the game's release, and while you may find a few holdouts here and there who are going to be playing the games for the first time and then branching out into alternate media to see what's out there, for the rest of us, it's "been there, done that, got the tabards."
Unless you're taking a very significant plot rewrite, there's not a whole lot you can do to tweak the events of the game. Which means that the only way someone can really put a spin on things is to "write for characters," i.e. take the same rehashed events and just gloss over them some, but have the main draw of the work come from the fact that this is a new character and a new perspective that you're writing from. It's through someone else's eyes, someone the collective readership hasn't seen before.
And maybe it's just me, and maybe it's just my experience, but it's why, I think, you tend to see more shorter works being successful than the "long-form" stuff.
Because it feels like the game's plot, as it is, has largely been mined out, but the characters? There's still plenty of material worth exploring, there. And that's why people keep coming back, using new protagonists to interact with those NPCs, putting those characters into settings aside from the tried and true. (Think Baldur's Gate... IN SPACE. Or Baldur's Gate... as a WESTERN. Or Baldur's Gate... in World War II.) I'd even argue that the actual plot of the game is pretty cookie-cutter. It's a fairly typical "You're a nobody who has his village burned down and has to grow up real fast in order to fight the big bad that's threatening to destroy the world." type of deal. Done a thousand times. But it's the cast that keeps us all coming back for more.
Edited by AlphaMonkey, 27 June 2011 - 08:10 PM.