SHOCKER: Social media clout doesn’t translate into book sales.

A book by Billie Eilish seemed like a great bet. One of the most famous pop stars in the world, Ms. Eilish has 97 million followers on Instagram and another 6 million on Twitter. If just a fraction of them bought her book, it would be a hit.

But her self-titled book has sold about 64,000 hardcover copies since it came out in May, according to NPD BookScan, which tracks most printed books sold in the United States — not necessarily a disappointing number, unless Ms. Eilish got a big advance. Which, of course, she did. The book cost her publisher well over $1 million. . . .

An author’s following has become a standard part of the equation when publishers are deciding whether to acquire a book. Followings can affect who gets a book deal and how big an advance that author is paid, especially when it comes to nonfiction. But despite their importance, they are increasingly seen as unpredictable gauges of how well a book is actually going to sell. Even having one of the biggest social-media followings in the world is not a guarantee.

Here’s the thing: Social media doesn’t have a lot of effect on the rest of the world. Facebook drives some traffic to sites, but in my experience not as much as it used to. Twitter never drove traffic. Instagram is designed not to drive traffic. Other sites like Tik Tok or Yik Yak aren’t any better. The thing about walled gardens is, the walls keep people in, and looking inward. Social media also cultivates an expectation for instant gratification, which books don’t offer.