A few weeks ago, I bought a copy of "The Second Machine Age" by two MIT researchers, Erik Brynjolfsson and Andrew McAfee, who are among the most insightful commentators currently writing about the likely impact on employment of advanced robotics, machine learning and big-data analytics. Since I already own more physical books than my house and office can hold, I tend now to buy the Kindle version of texts that are relevant to my work, and so it was with the Brynjolfsson and McAfee volume.

Yesterday, I received a cheery email from Amazon. "Hello John Naughton," it read. "An updated version of your past Kindle purchase of 'The Second Machine Age: Work, Progress, and Prosperity in a Time of Brilliant Technologies' by Erik Brynjolfsson is now available. The updated version contains the following changes: Improved formatting for readability. Significant editorial changes have been made. You can receive the improved versions of all your books by opting in to receive book updates automatically."

Note the phrase, "significant editorial changes have been made." In their book, Brynjolfsson and McAfee use Ernest Hemingway's observation about how a man goes broke — "gradually and then suddenly" — as a metaphor for what's been happening in the part of the technological world that concerns them. "Progress on some of the oldest and toughest challenges associated with computers, robots and other digital gear," they write, "was gradual for a long time. Then in the past few years it became sudden; digital gear started racing ahead, accomplishing tasks it had always been lousy at and displaying skills it was not supposed to acquire any time soon."