I've seen two major developments beyond the traditional published-once book. This article talks about one of them: "Unfinished", whether for fictional works with multiple editions or edited versions (as in this article), or for non-fiction references continuously updated to cover the latest version of the topic they document. However, this article still assumes a punctuated series of versions in essentially complete form, intended to be thought of as a complete book, even though the author may release a new version in the future.<p>There's a step beyond that sense of "unfinished": the future of the book is <i>in progress</i>, actively being written and edited. There's something particularly fun about reading the first few chapters of a book whose ending is <i>not yet written</i>, providing feedback, having a conversation with the author, and seeing that feedback reflected in the next update. See a typo, or a plot hole? Post a comment with a bug report. Having that experience with software was what hooked me on Open Source; however, that experience is not by any means limited to software, and it's quite a thrill for books (fiction or non-fiction) as well.<p>Having that feedback and update channel pervasively available really changes your outlook on prose, as it does with software. I've long since stopped putting up with software for which I can't file a bug report and ideally write a patch. Imagine a world where a significant fraction of books work the same way.