I am alternately fascinated and disturbed that books are getting their own trailers, just like movies. Now a book doesn't even have to be made into a movie to screw up how I imagine a character to look and sound!
Barnes and Noble's Studio is currently featuring The Art of Racing in the Rain by Garth Stein (which is on order at BHPL). Scroll down to see more, including one for Septimus Heap by Angie Sage.
You can see a trailer for Jodi Picoult's latest book, Nineteen Minutes, and other book trailers on YouTube. If there is a particular book you are looking for, like The Secret by Rhonda Byrne, just search for the author's name along with book trailer.
I'm not exactly sure that a book trailer is as useful as a friend's recommendation or a magazine's book review. Take a look at one for a book that you've read, and let me know if you think book trailers are faithful representations of books, or just slick promotional materials.