Since 2006, Philip Roth has been turning out short, devastating novels at the rate of one a year. “Nemesis,” his newest one, is a disturbing story about polio in 1944.

It’s a story about the enigma of misfortune. Plato called us playthings of the gods; Roth plays god with his characters, cruelly. And it sometimes seems as if he’s cruelest with those who are most blameless, like the “profoundly decent” young hero of “Nemesis.”

Bucky Cantor, 23, is the new gym teacher at a Newark school and the school’s summer playground director.

Mr. Cantor, as he’s called throughout — because the story is narrated by one of the boys who was under his supervision during the terrible summer of 1944 — is “the most exemplary and revered authority we knew, a young man of convictions, easygoing, kind, fair-minded, thoughtful, stable, gentle, vigorous, muscular — a comrade and leader both.”

He’s the kind of virileman Roth admires, and at the same time the kind of irony-free, less-than-brilliant good citizen for whom Roth doesn’t mask his pity and contempt.

The novel begins on a note of foreboding: “The first case of polio that summer came early in June “

There’s beauty — in the charming depiction of Mr. Cantor’s romance with a first-grade teacher named Marcia Steinberg; in descriptions of the landscape at a Jewish sleep-away camp in the Poconos; and in the lush, unhurried prose.

But in this book the beauty is muted.

“Sometimes you’re lucky and sometimes you’re not,” the author writes, laying out his theme near the end. “Any biography is chance, and, beginning at conception, chance — the tyranny of contingency — is everything.”