But there's a work around. Here's what you have to do.
Step 1: Create a new iMovie '11 project and drag all your photos that you want to use into it. I made sure each photo was 6 seconds long.
Step 2: Next set the Ken Burns Effect for each of the photos.
Step 3: Export the slide show as a movie
Step 4: Import the movie back into iMovie '11 as a new event.
Step 5: Now you're ready to make a book trailer. Make a new project and choose whatever trailer template fits your needs. Select the scenes from your imported event as you see fit.
Maybe it's because I'm kind of sick of the trailer templates that come with iMovie '11, but I found that iMovie for the iPad have more interesting and useful templates for this kind of project. They seem to use text more, which allows for a better story to be told through words and pictures. I did steps 1 through 3 on my laptop, so to make the video available to the iPad, I imported it into iPhoto, and then synched my iPad to it. I made the following book trailers for the first Skippy Jon Jones book on the iPad:
iMovie for iPad: The Retro Style Trailer
iMovie for iPad: Bollywood Style Trailer
After the jump, I have a trailer from iMovie '11
iMovie '11: Sports Style Trailer