“The Last Train From Hiroshima” is a clear-eyed catalog of every such horror, and not for the weak-stomached. Mr. Pellegrino follows his survivors as they trudge through wastelands that make “The Road” by Cormac McCarthy read like “Goodnight, Moon.” He describes the so-called “ant-walking alligators” that the survivors saw everywhere, men and women who “were now eyeless and faceless  with their heads transformed into blackened alligator hides displaying red holes, indicating mouths.”

The author continues: “The alligator people did not scream. Their mouths could not form the sounds. The noise they made was worse than screaming. They uttered a continuous murmur  like locusts on a midsummer night. One man, staggering on charred stumps of legs, was carrying a dead baby upside down.”

Image Charles Pellegrino Credit... Sarah Shatz

Mr. Pellegrino, whose many previous books include “Ghosts of the Titanic” (he also served as a scientific consultant to the director James Cameron on his Titanic expeditions and on “Avatar”), relates many stories in this book, not only those of wounded survivors but also of American and Japanese pilots and many others.

He pays particular attention to forensic detail, and provides a slow-motion, almost instant-by-instant explanation of how the atom bomb discharged its fury. There is not a lot that is new here, but “The Last Train From Hiroshima” is a firm, compelling synthesis of earlier memoirs and archival material, as well as of the author’s own interviews and research. This is gleaming, popular wartime history, John Hersey infused with Richard Preston and a fleck of Michael Crichton.

This isn’t a book that wrestles deeply with the moral calculus of the decision to drop the atomic bombs. Mr. Pellegrino doesn’t say whether he agrees with Paul Fussell, who wrote in “Thank God for the Atomic Bomb” that “the degree to which Americans register shock and extraordinary shame about the Hiroshima bomb correlates closely with lack of information about the Pacific war.”

But he certainly studies every kind of fallout and does not neglect the spiritual variety. He writes about one doctor who “recalled that those who survived the atomic bomb were, in general, the people who ignored others crying out in extremis or who stayed away from the flames, even when patients and colleagues shrieked from within them.”