The Times (the proper London one, not that New York pretender) is reporting that Nintendo has signed a deal with publishers Harper Collins related to its new ebook collection for the DS - 100 Classic Book Collection.
The article seems to imply that Harper Collins are just helping Nintendo get the 'classic' books onto the DS, but all of the books on the cart are in the public domain and available in electronic form via the Project Gutenberg, so one has to assume that the publisher will be providing some of its own catalogue of titles for future download or cartridge release.
Currently an additional 10 titles (all free) are up for download via Nintendo WiFi. Although the DS screen is a good deal smaller than that of the Amazon Kindle or Sony Ereader, it is also a good deal cheaper and has the added benefit of AWESOME GAMES. It will be interesting to see how this one plays out.