The decision to create a book trailer is entirely up to you. I can remember when "video killed the radio star" on MTV and how excited I was with some music videos (the ones that lived up to or exceeded my imagined vision of the song) and the ones I disliked so much, I even stopped listening to the song (the imagery just ruined it for me!) Some people argue that in a visual landscape, a book trailer is a must, while others stand firm that books should be read and not seen; unless of course it gets made into a screenplay and then a film. The most practical advice is to trust your instinct. You know what you want to say with your book and if it aligns congruently with your brand, then for a non-fiction book it may be a strategic move. On the other hand, it may come off as too "salesy" and go in the opposite direction. As you can see, I still have a love / hate relationship with matching someone else's images to my own imagination. No matter what you decide, remember to keep it aligned with your brand.