Five years ago, Mark McGurl was opening yet another Amazon box when he started thinking about the corporate behemoth’s impact on the novel. Amazon’s impact on bookselling was already widely acknowledged—anywhere from 50% to 80% of book purchases in the US are now made via the company—less considered was its effect on the very form of the novel.

McGurl, a literature professor at Stanford University and the author of Everything and Less: The Novel in the Age of Amazon, dove into Amazon’s most read (and unread) list. Through self-publishing programs like Kindle Direct Publishing, Amazon has allowed thousands of writers to bypass traditional gatekeepers. The result is an unfathomable volume of books. “If we’re talking about the numbers published, then we are in a golden age of ...