There's a general rule in technological innovations that once something hits the fifty percent market share, the game becomes basically over, and the tech will take over 90 percent plus of the market (at least until the next tech innovation.) If that general rule is correct, books (hardcover and paperbook) will all soon pretty much disappear thanks to Amazon's Kindle:
"Amazon has revealed that it has sold more Kindle ebooks than paperbacks in the US during the final three months of 2010.
A similar pattern has continued during January 2011 with 115 ebooks being sold for every 100 paperbacks.
The figure only relates to the US market and the number of ebooks sold on Amazon’s own e-reader device, the Kindle, which now accounts for 41.5 per cent of the e-reader market. Amazon is expected to sell more than eight million Kindles this year, up from 2.4 million last year, according to Bloomberg."
Amazon Kindle ebooks outsell paperbacks
28 Jan 2011