I can see a short story used to introduce new characters or background for a current character to support an on going series. On the other hand, I have read some where the publication of a short story for a book series is just a filler, either to fill for extended time between releases, or to try to keep the reader interested in the book series. (or just for a couple extra $$). When Stephen King did it with The Green Mile, I am not sure if he was just goofing with us and it was a different way to release a book or if he testing the waters for another short story ( chapter releases), like The Plant. whatever happened with that anyway??? By the way, I am not includng the release of a complitation of short stories, ie; The Skeleton Crew, The Bachman Books ( again with Stephen King, I know). I just finished Deep Down: A Jack Reacher Story. I give Lee Child credit because he is a good writer, but I am not sure where this fits in to his series. The Second Son was good for background, it made sense, but with this one, enjoyed it, but not sure about the timing. Guess when his next book is released will see if there was a point for this release.