I have to admit I’m a bit puzzled. Initially I was selling more e-books through Kindle and then people started asking me if a print version of my most popular e-books were available. That’s when I formatted my e-book as a print-on-demand book through Amazon’s CreateSpace. I absolutely did not think print-on-demand books would sell since they cost more, take time to ship, and take up space. Yet in the past few months, I’ve been selling twice as many print-on-demand books than I have e-books.
This may be unique to my particular book topics since I mainly focus on screenwriting. I suspect many people prefer a printed copy of the book, even if it costs nearly twice as much, simply because my book is a reference. As a reference, it’s probably easier to have something you can grab and flip through the pages to find what you want, rather than search through an e-book using a tablet or smartphone.
Does this mean print-on-demand is the way to go for self-published authors? Probably not. The bulk of self-published, e-book authors make money through romance fiction, which are basically throwaway type books that you don’t want to necessarily keep or even look at ever again. When you have basically disposable books, e-books are probably the better market. When you’re writing reference type books, then print-on-demand books are probably better.
Of course, I still sell the same book as both an e-book and print-on-demand book, so don’t think you have to choose one or the other. You just have to find what works for your particular market and use my experience as a guideline. As a general rule based on my own experience, reference books are more popular as print-on-demand books while light fiction seems better suited for e-books.
Since print-on-demand and e-books are both free to create, you might as well do both. Just expect sales to come from one side than the other no matter what your topic may be.