I can`t believe that there are some problems with book about game universes...But it would be nice to see and read epic book about Divinity Universe..
Have you read or read about the two I mentioned? Messing with how people played your game by retconning their actions (and then picking the one least liked outcome at that) and making that canon is a terrible idea.
Also there are some things in Mass Effect 3 (I think, not sure anymore, could have been Dragon Age 2 too*), that don't make sense if you haven't read the books and/or some comics. I'm not talking about minor references to outside events (like running into Drizzt in Baldur's Gate 1 & 2, that was OK), but parts of the plot that you just don't grasp due to missing information.
This is a terrible way to squeeze money out of people, if the game's content cannot 100% stand on itself without external sources you have either failed as developer or you are a jerk trying to squeeze cash out of your fans (hello EA!). Now, I don't think there's much risk for the latter case with Larian but the former could always happen (maybe with the best of intentions)
*still need to replay ME3 to see the "new" ending, maybe I'll take notes this time and cook up some kind of review or something. Maybe. Assuming I can ever find the motivation to go through that game again.