Books aren’t movies. They are words on paper. Or pixels on a reading device. Do books really need to have trailers like movies? Apparently they do, if you want to catch someone’s eye. Readers have changed. They have a gazillion things snatching at their attention. Books need to reach out and join the snatchers. So I’ve been told by a number of sites, anyway.
There are many ways to go about this, depending on your budget. If you’re confident your book will support a big budget, go for broke! Write an action sequence. Hire actors and a narrator. Maybe even a director. Scout out locations. Consider using a drone for overhead shots. Buy the rights to an expensive sound track.
Or you can do it for a lot less, like I did. Buy still images or videos from stock photo houses. Buy some stock music for your sound track. Narrate it yourself, or skip the narrator altogether and just use titles on the screen. Get some help editing the whole thing together. (My daughter helped me with my trailer.)
Here’s the result: https://www.youtube.com/watch?v=7QG1l6CgPSE