One of the challenges for book publishers, especially non-fiction publishers, is to keep their books relevant as the rate of change increases. The first market to see this play out, ironically, was computer books. Computer books were one of the fastest-growing and biggest segments of non-fiction publishing from the mid-1980s to about 2000. However, as product development cycles sped up, it became harder for publishers to recover their investment in individual titles, or even to get their books to market before they became obsolete. It takes most legacy publishers a year to get a book from manuscript to distribution, but in the first six months of 2012, Google released five major versions of the Chrome browser, and the Mozilla Foundation released four major versions of Firefox. There's no way that any publisher can keep up with that rate of change.
The rate of change has also increased dramatically in many other areas, including science, engineering, medicine, politics, economics, social sciences and business. Apply this test: If it takes 12 months to get your book from a completed manuscript to bookshelves, or if it even takes just 12 months from the conception of the book to bookshelves, will it be obsolete before it gets there? If the answer is "Yes", it makes no sense to produce a conventional print book. If you want to do a book and not a website or wiki, the only viable way to get to market quickly is to produce an eBook.
Once an eBook is published, however, it's subject to the same rapid aging as print. An eBook on Firefox 10 that was released the same day as the browser, January 31, 2012, technically went out-of-date less than two months later, when Firefox 11 came out. Non-fiction books need to be updated quickly, not just due to errata, but because the underlying facts can change so quickly.
By and large, print books are updated by printing a new version and throwing the old version out. eBooks, on the other hand, are bits, and bits can be changed easily. However, most eBooks sold today are simply digital equivalents of print--they're static and aren't designed to be updated. What we really need are "live books"--books that can be dynamically updated by the publisher in order to keep them fresh and accurate. A few publishers have begun to go down this path: O'Reilly Media, for example, gives customers who buy eBooks from their website free updates for the life of the edition. I buy O'Reilly's eBooks directly from the publisher, and pay a higher price than I would if I purchased them from Amazon or Barnes & Noble, in order to get those free updates.
O'Reilly isn't able to update the eBooks "in place"; they notify customers about new versions of their eBooks via email. Customers then have to log into the O'Reilly website, download the new version and delete the old one. Wouldn't it be better if O'Reilly could send an email that says that there's an update available for one of my eBooks, and that the next time I open up my eBook reader, there's a button on the front of the cover icon for that title that says "Update?"All I'd need to do is press the button, and the eBook would be automatically updated. The obvious next step would be for the publisher to automatically update eBooks without user intervention, but there should always be a mechanism for customers to specify whether they want automatic or manual updates, just as Microsoft Windows and Apple's OS X allow users to either manually or automatically apply updates.
Update June 29, 2012: O'Reilly has just launched a new service that synchronizes new versions of its eBooks with customers' Dropbox accounts, which will eliminate the need to manually download new and updated eBooks and copy them over to other devices. (eBooks on devices not supported by Dropbox will still have to be updated manually.)
There's clearly value in automatically getting updates to eBooks--and there's also value in getting updates that cross editions. For example, let's say that you've published a series of eBooks on Adobe's Creative Suite. Now that Creative Suite 6 is out, you could offer buyers of earlier editions of the titles the ability to upgrade to the new edition at a steep discount. Or, you could set up a subscription plan, which would enable buyers to subscribe to new CS books as they come out. The updates would work just as described above, so customers could keep the older versions of their eBooks until they're ready to update their software, at which time they'd have both the latest software and manuals.
Live books would merge eBooks, eCommerce and subscriptions to create non-fiction libraries that never go out of date and can generate income for publishers for years.