For the most part, a script for your book trailer should be an expansion on your pitch line and/or summary. Preferably with a little more emotional hook thrown in. The great thing about book trailers is that pictures really are worth a thousand words. Working in a visual media means you don’t have to worry about how many words it takes to describe your hero or the world he inhabits: your visuals should do that for you. Music can also provide a lot of dramatic mood. For example, let’s say you’ve got a short horror story about a haunted mansion. Imagine a panning shot of a mansion in the dark woods while creepy music plays. And maybe you animate a little fog while the main character provides a voice-over (or writes in their diary and the text appears across the screen.)
1. Don’t write blocks of text. I came here for a book trailer, not to read a book. This might be hard for writers to grasp, but it bears repeating: you’re working in a visual media. Take advantage of the shiny. Make things dramatic, fast, slick, and fun. A little text is fine, especially if you’re not a voice actor and don’t have access to a quality microphone. It’s just that if you think pasting your query letter into a Youtube video and flashing the book cover at the end is going to work, you’re totally missing the point. Remember to keep your dynamics rule in mind, too: if text must appear, make it interesting. For example, if your story is high fantasy, why not have your text appear like it was being written by a goosefeather pen? Or if its a noir tale involving a gritty reporter, let the words type out, with even some typewriter sound effects? This leads us to our next point.
2. Approach the script as though the trailer was part of the book’s world. For about two seconds when I was brainstorming for my trailer, I almost went the exposition route; i.e. “In setting place of epic sci-fantasy, main character must do this arbitrary thing …” Then I realized my story had pretty interesting elements on its own, and that I should try and attract readers with the psychic dolphin aspect of it. Your trailer should provide a snapshot of the characters and their world, in addition to their emotional stakes/the stakes of the story. You’re better off taking a scene from the book and turning it into the book trailer than trying to summarize everything. Since most books are A+B=C (Character Wants+Obstacles=Conflict/Story), three beats is not that hard to get in a minute. (Which about the length you should shoot for, although some trailers can go longer.)
I want to dedicate a blog to exploring sound for your book trailer, so stay tuned.