While the body counts mount in Afghanistan and Iraq, another military tally, less wrenching and tragic but poignant nonetheless, quietly proceeds. Every day more than 700 veterans of World War II die, and with each one goes a story, or dozens of them. Laura Hillenbrand reached Louis Zamperini just in the nick of time — he was in his mid-80s when she found him, and 93 now— and it’s an excellent thing, for his is surely one of the most extraordinary war stories of all.

In late May 1943, the B-24 carrying the 26-year-old Zamperini went down over the Pacific. For nearly seven weeks — longer, Hillenbrand believes, than any other such instance in recorded history — Zamperini and his pilot managed to survive on a fragile raft. They traveled 2,000 miles, only to land in a series of Japanese prison camps, where, for the next two years, Zamperini underwent a whole new set of tortures. His is one of the most spectacular odysseys of this or any other war, and “odyssey” is the right word, for with its tempests and furies and monsters, many of them human, Zamperini’s saga is something out of Greek mythology.

That story encompasses an aspect of the American experience during World War II — the cruelty of the Japanese — that, in an era of Toyotas and Sonys and Hideki Matsui, has been almost entirely forgotten. (Forgotten in the United States, that is: Japanese sensitivities on the subject remain sufficiently high that Hillenbrand refuses to identify her translators there.) It’s also yet another testament to the courage and ingenuity of America’s Greatest Generation, along with its wonderful, irrepressible American-style irreverence: just hearing the nicknames — many unprintable here — that the P.O.W.’s bestowed on their guards makes you fall in love with these soldiers.

The author of “Seabiscuit” — the story of a very different, and far less important, kind of miracle — Hillenbrand is particularly well suited to tell this inspiring tale. Apart from a rocky beginning (when, seeming to lack confidence in her main character, she hypes him), she is intelligent and restrained, and wise enough to let the story unfold for itself. Her research is thorough, her writing (even on complicated, technical wartime topics) crystalline. “Unbroken” is gripping in an almost cinematic way. In only one sense does it disappoint, but it’s important: that is, in its portrait of the hero himself.