I made my Evidence-based Software Engineering book available as a pdf file. While making a printed version available looked possible, I was uncertain that the result would be of acceptable quality; the extensive use of color and an A4 page size restricted the number of available printers who could handle it. Email exchanges with several publishers suggested that the number of likely print edition copies sold would be small (based on experience with other books, under 100). The pdf was made available under a creative commons license.
Around half-million copies of the pdf have been downloaded (some partially).
The printed version looks great, with vibrant colors, and is reasonably priced. It sits well in the hand, while reading. The links obviously don’t work for the paper version, but I’m well practised at using multiple fingers to record different book locations.
I have one report that the Kindle version doesn’t load on a Kindle or the web app.
If you love printed books, I heartily recommend the paperback version of Evidence-based Software Engineering; it even has a 5-star review on Amazon