I got the following email this morning that astounded me. I thought I'd share (with the author's permission):
Just dropping a line telling you I like your WPF Unleashed book a lot, and brought it to my recent trip to Tibet. I also took a picture of your book in the wild, and thought you might like the photo!
Luc (Paris, France)
Looking through the photo album, I uncovered this photo as well. I guess the book can be used for many things!