Star Wars, Catalyst : a Rogue One novel / James Luceno.

War is tearing the galaxy apart. For years the Republic and the Separatists have battled across the stars, each building more and more deadly technology in an attempt to win the war. As a member of Chancellor Palpatine's top secret Death Star project, Orson Krennic is determined to develop a superweapon before their enemies can. And an old friend of Krennic's, the brilliant scientist Galen Erso, could be the key. Galen's energy-focused research has captured the attention of both Krennic and his foes, making the scientist a crucial pawn in the galactic conflict. But after Krennic rescues Galen, his wife, Lyra, and their young daughter, Jyn, from Separatist kidnappers, the Erso family is deeply in Krennic's debt. Krennic then offers Galen an extraordinary opportunity: to continue his scientific studies with every resource put utterly at his disposal. While Galen and Lyra believe that his energy research will be used purely in altruistic ways, Krennic has other plans that will finally make the Death Star a reality. Trapped in their benefactor's tightening grasp, the Ersos must untangle Krennic's web of deception to save themselves and the galaxy itself.