I think authors are as bewildered as anyone else as far as what works for promotion and what doesn't. I don't know that book trailers sell books, but they're relaxing to work on. What's not to enjoy about matching pictures to music and mulling over the important elements of your story?
Anyway, I worked on three trailers yesterday, and this one is the only one that seemed acceptable to me. (The SO looked at it and said, the music should have been the music of the era, but I really like the juxtaposition here -- and the soundclip, a bit of a song, by Muse, is absolutely perfect for Nathan's state of mind.)