Okay, let me qualify that. If by ruin you mean "bring an end to" and if by book publishing you mean the "careful and professional preparation and dissemination of long form intellectual property expressed in words" then I stick by my answer and say, of course not.
Now if by book publishing you mean the above definition but specifically and predominantly in a paper, ink, and binding medium, then I guess the answer is possibly. Maybe the readers of the world will gradually or spontaneously decide that we don't need to kill any more trees and that electronic dissemination and acquisition is the only way to go. First, I would say that in the world of book publishing content is king and packaging secondary - a tough admission from someone who makes a living as a gift book publisher. So if paper, ink, and binding some day go away, I would simply say, no big deal. I don't think that's going to happen any time soon as the latest research (the PubTrack program from Bowker) indicates that 82% of Americans - who represent one third of the book publishing market - still prefer printed books exclusively.
In his book Business At the Speed of Thought Bill Gates asserted that we tend to overestimate the amount of change new technology will cause in its first two years but underestimate the amount of change that will occur in the next five years. How long has Amazon had the Kindle and Sony its e-book reader in the market? If Gates was right then it will be 2012 or 2013 before we have a pretty good idea where e-books are going.
Now if by book publishing your definition is closer to "long form intellectual property expressed in words" no matter what media is used to distribute the material then I would say for that to come to an end some entirely different dynamics other than an e-book reader would have to be involved. Mike Hyatt, CEO of Thomas Nelson and my boss, raised the question of what the Internet is doing to our brains in his blog, particularly in relation to its impact on long form reading. He cites Nicholas Carr's article in the Atlantic Monthly, "Is Google Making Us Stupid?" Carr's observation is that as the Internet has become his universal medium, concentrating on longer pieces for more than a couple of pages has become increasingly difficult. Carr says:
I’m not the only one. When I mention my troubles with reading to friends and acquaintances—literary types, most of them—many say they’re having similar experiences. The more they use the Web, the more they have to fight to stay focused on long pieces of writing.
Since an e-book, at least in its most popular hardware expressions, is designed to essentially look, feel, and behave like a a paper, print, and binding book, you can't blame it for any for any widespread impact on people's ability to apprehend long form content just because it's in a digital format.
Again, citing the most up-to-date research from Bowker's PubTrack data, in 2007, 164 million Americans over the age of 13, about 75% of the population with discretionary spending power, purchased at least one book. Book consumption is greater with age but still relatively constant. And for those who assert that junior readers simply won't read unless the content is wrapped up in a digital sight, sound, and interactive experience, I'd simply point to the Harry Potter phenomenon where seven- and eight-year-old kids could suddenly read 800-page books! There is an ongoing voracious appetite for books across ages and within all the niches of the human marketplace. And America won't always account for one-third of all book consumption.
So will e-books ruin book publishing? Absolutely not. Will they change book publishing? Over time, most likely, but not in its essence.
So book publishing, a medium brought to the masses by Johannes Gutenberg through his invention of mechanical printing almost 600 years ago, is safe for at least another millennium?
Now that's an entirely different question! Give me a sec and I'll see if I can google an answer!