Star Wars: Catalyst: A Rogue One Novel by James Luceno
The Republic and the Separatists have been battling each other in a galactic war. No one is spared as each side scrambles to gain the edge against their enemy. Working for the Empire, Orson Krennic is working on a top secret project–a planet killer. But while he throws every available resource at his command into the project he realizes there is one thing he is missing–his old friend Galen Erso.