This time it comes from Publishers Weekly’s article about the effect of NYTimes reviews on non-fiction titles. Reading the article, it seems clear that reviews on their front page for books that weren’t already planned to be blockbusters were worth nothing more than a few hundred sales on the week it came out, with the exception of one book on economic inequality. That book not only sold well on the week it came out, but sales continued to go up.

What does it mean? Well, inequality is one of the more popular ways of talking about our political problems at the moment, so I’m guessing the readers who were prompted to snap up that book on the week it was reviewed started telling others about it.

In other words, the review was only useful because it helped spur the only marketing that really matters: readers talking to readers.