I see that somebody is selling a course for self-published authors on how to make "Hollywood-style" book trailers.
I don't think that's a very good idea. Reading a book is a different process from watching a movie. A trailer is a sample of the full movie-viewing experience, it's not a sample of the full reading experience.
Authors of non-fiction have it easier. If, for instance, your book is about cooking, you can make a trailer that includes some cooking tips. Viewers will know that if they like those tips, they'll get more like them in your book.
If your book is about space travel, you can build a few fun facts about that in your trailer. If they buy your book, they'll learn more about that topic.
However, if you've written a novel, there's not the same kind of link. Yes, if it's a mystery in which the protagonist is a chef, you could include a cooking tip but people don't buy fiction for tips. Similarly, viewers wouldn't read a sci-fi novel primarily for facts.
I've seen book trailers in which authors are interviewed (or interview themselves) about what inspired them, their research process, etc. Unfortunately, people are likely to find that interesting only if they've already enjoyed the book or know you from other things you've written. Sorry to be brutal, but otherwise nobody cares.
Even non-fiction authors who make a trailer for their book are left with the big question: how do you get people to watch it? Put it on YouTube? Here's a little quiz:
In 2014, Youtube said 300 hours of new videos were uploaded every:
You probably guessed right--300 hours every minute! That's not to say you can't get your target audience to watch your YT video, just that it's not easy.
The bottom line: if you're a self-published author of fiction, there are better ways to spend your money than learning how to make a book trailer or on a trailer itself.