What is the author's style in Hiroshima by John Hersey?

The text is delivered as an extended piece of journalism originally intended for serial publication in a widely circulated periodical. After writing, the text was presented in a single issue of the periodical and, later, was published in book format with minor revision. Subsequent editions appeared and approximately four decades after initial publication a second edition was published containing a substantial volume of new material. The author, a journalist by trade, intended the text to be a recital of facts about, and a tribute to, the survivors of the first nuclear detonation.