For years, the norm was that books adapted into movies were typically brought to the silver screen with minimal, if there was any at all, assistance from the author of the original text. Perhaps because of long-time dissatisfaction with how these works were adapted or perhaps as a way to mimic the success Marvel Comics had with taking control of film adaptations of their own characters, authors like Mark Millar, Seth Grahame-Smith and especially Patrick Ness (who adapted his own books A Monster Calls and Chaos Walking for the big screen) have recently become more involved in how their works become translated to the world of cinema.
