Scanning of paper books and making them available online to everyone is inevitable. Lib.Ru is a large decade-old grassroots Russian project with about 40000 copyrighted and public domain books. Project Gutenberg is a repository for public domain texts with 16000 books.
"Envisional, a company based in Britain that tracks Internet piracy, estimates that 25,000 to 30,000 pirated titles are available on the Web."  Dedicated book pirates exist that can coordinate their efforts to quickly release popular books online .
Some sites (Amazon, Google) have partially or fully scanned a lot of books, but these aren't freely available. Google also intends to mass-scan books from US libraries.
TeleRead is a organisation advocating national digital library system for the US.
Many organisations abroad, especially in the non-English speaking countries have their own plans for national digital libraries, particularly, France and Russia.
There is no definite timescale, but by 2015 we can expect a very large share of printed works to be available online, much of it for free.
While they’ll be sold as computers, the tablet PC and its successors will finally give consumers a true surrogate for the printed page and thus put high-quality “book players” into millions of hands, making low-cost electronic distribution of books a reality. Readers will have a far wider range of titles to buy and will, moreover, be able to communicate more freely with authors and other readers. Publishers can supplement the “word of mouth” marketing that has always been a key element in book-selling with online reader forums, sophisticated rating systems and collaborative filtering technologies. Books may actually live or die on their merits, rather than lucky publicity.
In short: the Internet presents all the elements needed for a true reinvention and renaissance of book publishing. But both readers and writers will need to be patient, because publishing—the oldest mass medium—will almost certainly be the last to take advantage of the newest. Source