Technically speaking, this Hellboy cartoon isn't a "book trailer," but an animated adaptation of a comic book that serves as prologue to The Golden Army, the movie that opens at the end of next week. But I think there's a pretty interesting takeaway for certain types of fiction writers here...

Usually, when I've talked about using the storytelling power of book trailers, it's been about making a promotional film that introduces or summarizes the plot of the novel or the central theme of the nonfiction work. This film, however, shows us another alternative: backstory.

Science fiction and fantasy authors, romance novelists, and mystery series writers—among others—might be able to create a trailer out of material that didn't make it into the final manuscript, but helped them figure out what that story was. Maybe it's an incident in a character's past that's barely hinted at, or a quick history of the political infighting within a galactic empire, or just a scene that got cut because you needed to lose 10,000 words... The point is this: As the author, you know more about your stories than your readers—but one of the ways that readers can become "True Fans" is when they feel you're sharing more with them than what's in the book. Romance writers have this principle down solid; among other things, they'll sometimes write "bonus stories" revisiting favorite characters for their online fans. But what is used as a reward can also be used as an inducement...

(spotted on io9)