It seems like it to be honest. Writing a book is like taking a snapshot of the industry you are writing about at that very time. Let’s say that you are writing about the ever changing search industry. The tips that you are giving to your users could be outdated in the matter of weeks, but your book stays the same way until you decide to publish the next edition. At some point people are going to stop buying your old book, and you are pretty much stuck with your publisher to get your new edition rolling. I think that’s why many people are now moving from the fixed-fee business model to the subscription-based business model.
Take Aaron Wall for instance. He has probably the best search engine optimization book in the industry. To be fair to him, he did update his eBook numerous times to keep offering his students the latest info on search engine optimization. But in the end you are fighting the inevitable. The effort that goes behind updating a book numerous times is too much to be quantified by a one-time payment. Think about it. If Aaron asked you to pay a one-time $1000 fee for his book, would you? If you are a SEO freak, you probably will. But paying a $1000 for a book seems unreasonable. That’s where the subscription model comes in. You can charge a monthly fee of let’s say $30 and constantly provide your readers with up to date information. The best thing about this is that the readers are not stuck with old content. At the same time, the writers can get paid for their effort to keep their books up-to-date. Book on demand is not where software on demand is right now, but you can expect it to catch fire in the near future especially with devices such as Amazon Kindle.