The adage says not to do this. While it’s certainly true that bad books can have good covers and bad covers can camouflage bad books—the Big Five publishing conglomerates are guilty of both sins—a better adage might be “a better cover makes any book look more attractive to read.

The “need” for a cover comes from print versions, of course. A traditional book without a good cover doesn’t look more than a manuscript, some legal document, or battle plan (“Project 2025”); in other words, it looks lik...