Sheinkin wanted Bomb to be historical nonfiction that almost reads like a novel, which makes identifying the narrative technique a bit tricky. Sure, we're offered glimpses into the thoughts and motivations of several of our characters, but we only ever get this info from direct quotes and interpretations of primary sources.
Because of this method, it can sometimes be hard to really relate to the characters in the story. At times the book comes off as a bit emotionless or cold, but this is because it basically sticks to the facts rather than sensationalizing real people. For example, a pivotal moment in our main character's life is written like this:
The meeting changed Oppenheimer's life. From that moment on, he knew he'd found his role in what was becoming a global showdown. "I spent some time in preliminary calculations about the construction and performance of atomic bombs," he said, "and became increasingly excited about the prospects." (Rapid Rupture.(5).17)
In short, because of Sheinkin's desire to be clinical and accurate, we're left to interpret the emotional ramifications of such a life-changing moment on our own.