Just to be completely unfair, I'm going to contrast the video in the book trailer of the previous post with this one.
See? That's how video and voice over should be, if you are going include them. Of course, the budget for this was probably larger than the budget for my wedding, because we are talking Robert Jordan and Brandon Sanderson. Tor could afford to make this look good. It's pretty hard to compete with the flagship title for a major publisher. Still, it gives all of us little guys something to aspire to.
Oh, and I have this theory that the sweet spot, length wise, for a trailer, is 70 seconds, or one minute, ten seconds. Notice the length on this one.