T wenty-five years ago, I published my first book, The Tipping Point: How Little Things Make a Big Difference. Back then I had a little apartment in the Chelsea neighbourhood of Manhattan, and I would sit at my desk, with a glimpse of the Hudson River off in the distance, and write in the mornings before I headed to work. Because I had never written a book, I had no clear idea how to do it.

I wrote with that mix of self-doubt and euphoria common to every first-time author. “The Tipping Point is the biography of an idea,” I began, “and the idea is very simple. It is that the best way to understand the emergence of fashion trends, the ebb and flow of crime waves, or, for that matter, the transformation of unknown books into bestsellers, or the rise of teenage smoking, or the phenomena of word of mouth, or any number of the other mysterious changes that mark everyday life, is to think of them as epidemics.

Ideas and products and messages and behaviours spread just like viruses do.” The Tipping Point was published in the spring of 2000. The first stop on my book tour was a reading at a small independent bookstore in Los Angeles, to which two people came, a stranger and the mother of a friend of mine – but not my friend.

(I have forgiven her.) I said to myself, Well, I guess that’s it. But it wasn’t! The Tipping Point grew like the epidemics it described – at first gradually, then all in a rush.

By the time the paperback came out, it had entered the zeitgeist. D o .