I've been making book trailers for 4 years now.
Mine are simple.
No bells or whistles.
Just photos, music, and script.
My first one was Greetings from Nowhere:
Then The Small Adventure of Popeye and Elvis:
Then The Fantastic Secret of Owen Jester:
I'm currently working on one for my October release of On the Road to Mr. Mineo's.
Here are the steps to a VERY basic book trailer:
1. Find photos. I use iStock Photo. They always have great photos that fit my story. I download the small size. Each photo costs a certain number of "credits." The credits needed for this trailer cost about $180. I also sometimes use this site.
2. Find music. This is fun. You want the music, of course, to fit the tone of the book. I use Premium Beat because they have a good variety and are inexpensive. I bought the music for $30.
3. For this trailer, I also added one short video clip, purchased from iStock Photo for $20.
4. Write the "script."
5. I use iMovie. Easy peasy. Literally drag the photos and music into the project. Add transitions, etc.
6. I spent 5432 hours tweaking it.
7. Try to keep the total length of the trailer to no more than 2 minutes.
8. Publish to YouTube, Teacher Tube and/or Vimeo.
9. Spread the word online.