Every genuinely revolutionary technology implants some kind of "aha" moment in your memory -- the moment where you flip a switch and something magical happens, something that tells you in an instant that the rules have changed forever.

I still have vivid memories of many such moments: clicking on my first Web hyperlink in 1994 and instantly transporting to a page hosted on a server in Australia; using Google Earth to zoom in from space directly to the satellite image of my house; watching my 14-month-old master the page-flipping gesture on the iPhone's touch interface.

The latest such moment came courtesy of the Kindle, Amazon.com Inc.'s e-book reader. A few weeks after I bought the device, I was sitting alone in a restaurant in Austin, Texas, dutifully working my way through an e-book about business and technology, when I was hit with a sudden desire to read a novel. After a few taps on the Kindle, I was browsing the Amazon store, and within a minute or two I'd bought and downloaded Zadie Smith's novel "On Beauty." By the time the check arrived, I'd finished the first chapter.

Aha.

I knew then that the book's migration to the digital realm would not be a simple matter of trading ink for pixels, but would likely change the way we read, write and sell books in profound ways. It will make it easier for us to buy books, but at the same time make it easier to stop reading them. It will expand the universe of books at our fingertips, and transform the solitary act of reading into something far more social. It will give writers and publishers the chance to sell more obscure books, but it may well end up undermining some of the core attributes that we have associated with book reading for more than 500 years.