According to Forrester, ebook sales will reach nearly $1 billion in the US this year. That figure that will triple by 2015, at which point the industry will be "forever altered" the researcher said. Although most people still borrow books from a friend or the library, about 7% of 4,000 online adults read ebooks. While that may sound small, those individuals happen to read and spend the most on books.

"We have plenty of room to grow beyond the 7% that read ebooks today and, once they get the hang of it, ebook readers quickly shift a majority of their book reading to a digital form," said Forrester. The average ebook reader already consumes 41% of their books in digital form, and that's folks without a dedicated e-reader. Those with a Kindle or similar device read 66% of their books digitally.

Despite exploding sales, dedicated ebook readers aren't the most popular way to consume digital books. The study found that 35% of people who read ebooks do so on a notebook. Amazon's Kindle follows in second place at 32%, while the Apple iPhone, Sony eReader, and netbooks occupy the remaining top five spots. How frequently do you buy digital books and what's your preferred reading device?