Here’s an example of something authors can do now that was nearly unthinkable before digitization. E-books can turn on a dime, so authors can revise and re-publish as often as they like…up to the point where readers are annoyed if they must buy the update. For most books, it’s probably worth thinking ahead before pulling the trigger on an update.
If you’ve published a non-fiction, reference-type book, consider a companion website where readers can get updated resources and information. But if you do this, make sure and maintain the website (best to do this according to an announced schedule) or risk losing your audience.