The repository has 1.5 million books in over 20 languages so far, all of which are available free on its website.
This represents just one per cent of the world's books, but the team behind the project sees total digitisation as the way forward.
"Anyone who can get on the internet now has access to a collection of books the size of a large university library," said Raj Reddy, professor of computer science and robotics at Carnegie Mellon University.
"This project brings us closer to the ideal of the 'universal library' making all published works available to anyone, anytime in any language. The economic barriers to the distribution of knowledge are falling."
The scheme was set up primarily using staff and resources from Carnegie Mellon, Zhejiang University in China, the Indian Institute of Science and the Library at Alexandria in Egypt.
The US, China and India provided US$10m each in cash and in-kind contributions to the project, and 7,000 books are scanned onto the system daily by 1,000 staff. The bulk of the scanning is done at 40 specialist centres in India and China.
Protecting and preserving texts is the major goal, according to Pan Yunhe, leader of the Million Book Project in China, and former president of Zhejiang Un iversity.
"Paper gets old and brittle, and artwork fades, and books become so delicate that no one can read them without damaging them," he said.
"But once we have digitised texts and illustrations, we can keep them in circulation indefinitely. And by storing them at multiple sites, we can minimise the risk of them being destroyed, as occurred in Alexandria."
About half the works are out of copyright and open to all without charge.
Digital library hits 1.5 million volumes
By Iain Thomson on Nov 30, 2007 1:11PM