Making a Book Trailer: the music selection

When I'm in the creative process of making a book trailer, my first thought is music. If I don't have the right sound it throws off the entire project. I take in to account the mood of the book; if its theme is serious a peppy tune isn't going to help portray the mood to potential readers.

For example, when working on Carlene Havel's book trailer for her novel, A Hero's Homecoming, I knew the exact piece that would compliment her book.
Take a listen:

The Fallen, by Todd Harvey, has a military, sombre tone that fit the book's hero -- Rich, a Colonel returning home from war with some unpleasant discoveries to make -- to perfection.  This was a musical composition I'd heard months ago, and kept in the back of my mind for just such a project.

My way of thinking is: if the music doesn't fit the story line, it most likely won't pique the viewer's interest.