As Justin Cronin clearly knows, if you’re a writer seeking to slough off highbrow pretensions — to reject your early efforts at “quiet” fiction and write something with commercial appeal, something that will, if not conquer the critics, at least pay for your kid’s college education — you’d be wise to opt for a vampire novel. The genre has proved so indomitable that it’s a wonder the Balkan underclass, whose age-old folk tales began it all, hasn’t started to request royalties.

Cronin is a graduate of the Iowa Writers’ Workshop, and his first two books, “Mary and O’Neil” and “The Summer Guest,” were literary explorations of life’s quotidian challenges. His new one, “The Passage,” is a 766-page doorstop, a dystopian epic that’s the first installment in a projected vampire trilogy. Ballantine Books bought the lot for over $3 million, and the film rights to the novel sold before the book was completed. If there’s a class at Iowa on exploiting publishing crazes, Cronin surely aced it.

And in many respects, he has delivered the promised blockbuster. While it relies at times on convention, “The Passage” is astutely plotted and imaginative enough to satisfy the most bloodthirsty reader. It opens in 2018, as America is engaged in nonstop warfare, terrorists are attacking us at home, and a gallon of gas costs $13. In a secret project, the military has employed the research of a Harvard micro­biologist in hopes of engineering a race of superbeings who can master any skill in minutes and whose wounds heal almost instantaneously. Of course, the project backfires, and once these “virals” — vampires — are unleashed into the world, the human race is rapidly brought to near-extinction. The mutants are fast, hungry and unforgiving. They kill and they recruit.

Fast-forward nearly a hundred years: 94 people survive in a heavily fortified colony, kept safe from North America’s 42.5 million vampires by a system that eliminates the night. When the community realizes that the power source maintaining its dusk-to-dawn illumination will soon die, a renegade band ventures out into a world it knows very little about. (Not one of them, for example, has ever seen the stars.) Their quest to recharge the colony’s batteries is elevated to a hope to reclaim the world after they chance upon a peculiar girl who can communicate with the vampires and who, like them, appears ageless. Unlike them, she’s on the humans’ side.