“The book business is changing more radically now, and quicker, than movies or music or newspapers have, because we’re doing it in a matter of months,” he said. “In [the] next 24 months is when this business will totally shift,” implying that eBooks will dominate sales. (Note: In a post-conference follow-up, Parrish now says he didn’t mean to put a specific timeline on the shift.)

As evidence, he pointed to numbers from Codex Forrester and Gartner Research: 30% of all readers consume both ebooks and print books to some degree. For 2011, the company predicts 18 million ereaders will be sold — compared with just 900,000 sold in 2009 — and 35% of readers will own come to own one. As for actual book sales, the Association of American Publishers reported ebooks in the U.S. brought in $70 million last January, a 116% increase from the same month last year, while adult paperback sales fell from$104.2 million to $83.6 million during the same period.

Given those numbers, and the rapid pace of adoption, Parrish implies the industry will soon reach a point where more readers will prefer ebooks than print.

Just as the transformation in music and movies was rough, the shift in the book industry has been anything but smooth. Sure, Amazon and Apple are well-poised to benefit — Amazon (AMZN) reported in January that ebook sales passed paperback sales, and Apple (AAPL) has said 100 million ebooks have been downloaded via its iBooks store since last April — but traditional brick and mortar stores, including Barnes and Noble and Borders, the latter of which filed for Chapter 11 Bankruptcy protection last month, continue to struggle.

Even Google (GOOG), an Internet giant with no brick and mortar legacy to tie it down, is running into trouble. Earlier this week, a judge struck down a 2008 deal between Google and various author and publisher groups worth $125 million that allows the company to make millions of books available online.

If Parrish’s predictions are right and ebooks become the dominant book medium by March 2013, the question changes from who will come out on top, but who will get left behind in the newest race of technological relevancy.