the books relating to Assassins Creed mostly just tell the story of the game, the difference being that the story is told in a more fluid way. For example; where I might spend the next 10 years dicking around in Florence finishing up all assassination contracts, jobs and so forth the book relating to Assassins Creed 2 simply told the story of Ezio Auditore in a more fluid linear path. I've not gotten up to Assassins Creed 3 but I think the book relating to that actually tells a slightly different story, it tells it from the viewpoint of Connor's father, a Templar. I don't mind the Assassins Creed books, sure they're not the greatest literature out there but they're a good time killer on journeys or sitting at my desk in work.

Gears of War on the other hand, tells a lot of back story in books developing characters, in some cases Bernie for example you actually truly get to know and understand the character in the books because for the most part that is where her story begins. What I didn't understand after reading these books was the character of Jace. He doesn't seem to crop up anywhere apart from in Gears Of War 3. And in GoW3 he's treated as if we've known him since game 1. I'm all up for an expanded universe explaining a character origin but genuinely if you're going to introduce a new character in to an established franchise such as Gears at least put them in to one of the books from the expanded universe first. To me Jace feels like a desperate attempt to write more black characters in to the story fast.

So yeah done well, expanded universe is great. I mean don't forget, KOTOR is part of the Star Wars expanded universe, it flows both ways. However badly done expanded universe material needs to go die in a fire.