I finished Gears of War: Aspho Fields by Karen Traviss like I do most books, with a 100-200 page sprint that keeps me up until 3:00 AM. Traviss appears to have mastered (what I believe to be) the first rule of working in an established universe, and that is preserving the feel of the franchise.
Obviously, there are no brutal cutscenes to watch or bosses to fight. Instead, Traviss works on the familiar characters of Delta Squad and Colonel Hoffman, along with newcomer Tai Kaliso. In this, she appears to have mastered the second rule as well: Adding characters and backstory that fit into what we already know.