What makes a book jacket "work"? If you ask editors, publishers, designers and even authors, you'll get a lot of answers, about design and color and typeface and "point of view." A good book cover needs to catch the eye, of course, but it also needs to reflect the sense and sensibility of the words inside.

Sometimes, this is even harder than it sounds. In a book culture of huge buys and short space, a cover must telegraph all this, and more—and in a few short seconds. When a house is going out with a type of book it has rarely published before, the doubts multiply.

That was the situation last fall when Knopf set out to publish Kevin Guilfoile. Cast of Shadows, the debut novel by the McSweeney's regular, was hard to classify (thriller? sci-fi? whodunit?), but it had Big Book written all over it. The task fell to Knopf art director Carol Devine Carson and designers Peter Mendelsund and Abby Weintraub—and they sat down with PW to discuss the evolution of the jacket. In house, their directive was clear. "Our boss, Sonny Mehta, wanted to be able to compete in the mass market. Other imprints have a standard look that we didn't really want to emulate, but we wanted to appeal to the audience that buys these thrillers," Mendelsund said.

That "standard look" sells books to customers, of course, but also to booksellers. Knopf staffers contended that books that "got a treatment"—a euphemism for large type and lots of shine—would do better with a certain major-chain buyer. The chain would take significantly more copies if the buyer liked the cover, they said. How many more? "Thirty percent? Who knows?" guessed Carson. "It puts the fear of God into you," Mendelsund added.

Guilfoile's near-future novel is about a doctor specializing in cloning. When his daughter is murdered, he uses his expertise to clone her killer from evidence left at the scene. It's a complicated conceit—sci-fi, legal thriller, straight-up whodunit, with an action-packed real-time video game thrown into the mix.

The first iteration looked like classic Knopf. Others passed through the minted thriller combine. Something close to the final product was nixed by Guilfoile and his agent, Simon Lipskar. "They said, 'We don't want this to be a William Gibson,' " according to Mendelsund. " 'We want it to be more like a Michael Crichton.' " Mendelsund observed to himself: "Well, Michael Crichton wasn't Michael Crichton until Chip [Kidd] down the hall made him Michael Crichton."

Eventually, a final cover was born, which you see here. Turn the page to see eight of the other Cast of Shadows iterations. (There were dozens more.) "This is not a cutting-edge jacket," Mendelsund admitted. "It's not like the most beautiful thing in the world. The materials signal mass market, but the layout doesn't. It was kind of a compromise in the end."