There has been a lot of talk recently about the tablet that Apple may or may not be releasing on Jan 27th. One of the things that is speculated to be on the tablet is digital books which can be purchased like apps and music can be now. However I'm not here to speculate over what features the tablet might have, (others are doing a fine job of that) I just wanted to make a comment about benefits that digital books can have over physical ones.
One of the benefits of the App Store is what when the developer finds some bugs they can submit a patch and then the user can painlessly update their copy of the application. If digital books were sold through iTunes then they could be capable of doing the same thing. If there were errors in the text then when the author discovered them they could submit and update and all the users would then have a corrected version of the book.
Also is the books could have extras then the author would be able to submit other writings and information after the book is in the market. This would even book more useful in technical (or manuals) books which authors often try to release quickly after the product is released. Then they could add to the book and fix errors that are pointed out to them by their reader.