The going theory is (and has been for some time) that book trailers are dead. Completely. But the thing is, theories are broad strokes. True for a bunch, but not necessarily for everyone. One thing I've learned in the past few years is that promotion is (or should be) every bit as unique as the book being advertised. Just as everyone has a slightly different path to publication, we all also have unique paths to getting our books noticed. And if you listen too hard to the going theory, you just might count out a promotion avenue that could work incredibly well for you.
The trailer I put together for my MG, THE JUNCTION OF SUNSHINE AND LUCKY, literally has thousands of views, and is being used by both theaters and librarians to introduce the book to young readers. So of course I had to put one together for my next YA, SPARK, as well.
Here's another thing about not listening too hard to going theories: It means you gravitate toward promotional efforts that are just plain fun. And I had a blast putting this together: