Hillenbrand's books have been hailed as "meticulously researched and powerful." Unbroken, much like her first bestseller Seabuiscut, is written in a style that walks a fine line between objective and compelling. That is to say, as a biography, Unbroken is neither overly emotional nor is it too dry.
Hillenbrand chronicles Zamperini's life from his childhood as a trouble maker, through his transformation into a world class (Olympic) runner, to his years of survival as a seemingly unbreakable POW, to his recovery from the war as an alcoholic turned born-again Christian. She chooses to present facts chronologically and in vivid detail. While the main story focuses on Zamperini himself, she gives plenty of credit to the many people in his life who influenced him and ultimately helped him survive the war. Her writing is fluid and the long book reads relatively quickly, as she balances both the narrative and journalistic styles that make the story equally compelling and believable.
Hillenbrand reportedly spent seven years compiling meticulous research through personal interviews, news articles, letters, and anything else she could find that would provide relevant information to her story. In this way, her presentation of Louis Zamperini shows as much of his humanity as it does of his heroism in survival. She includes gruesome and vivid imagery in many of the more horrifying scenes, but maintains an objective voice throughout the biography, and does not write from any obvious sense of bias. In this way, the author maintains integrity as a biographer yet manages to weave artistry into her presentation of historical events and an historical figure. I think the bottom line is that Hillenbrand chooses to present Zamperini and his story factually, but with honesty, detail, and artistic justice.