R. J. Palacio, author of WONDER (which I thought was very good, overall) has now issued a short (88 page) ebook called The Julian Chapter, for £1.49/$2.51. It gives the viewpoint of the bully in the book.
The publisher says, "Thought-provoking, infuriating, surprising, heartbreaking and heartwarming, this is a must-read for the thousands of readers who loved WONDER."
I'm not saying Palacio did it for mercenary reasons only but it is a clever way to generate some extra revenue from people who are already fans.
This could start a trend!