An Aperture user over on the Apple discussion board wanted a way to print out "crops" of a single picture so that you you could print them out on 4x6 inch paper and paste them together to make a big picture. I interpreted this as an "art" project so I suggested the Aperture Book tool.
Instead of explaining it I just did a little tiny video. Actually if I were doing this I would probably zoom the images a bit and skew them as well just so when I put it all together the pieces of paper would be overlapping and crooked when the image was correct.
Enjoy. Be sure to up the resolution to 720p if you watch it large.