Microsoft has launched the PC version of its Microsoft Reader software designed to let users read electronic books.

The software giant also announced the opening of an online retail bookstore at, where Microsoft Reader books will be available for commercial download.

The Reader software can be downloaded for free from the Web at

E-books have so far proved to be a tiny percentage of the publishing business.

But industry watchers believe the Reader software will draw content into the new market and keep older titles available.

Out of print books that aren't commercially viable in print could now find a new channel to market.

In traditional paper-bound publishing, the product has to be printed, it has to be delivered, and it has to be warehoused. E-books effectively make the phrase 'out of print' obsolete.