My six-year-old was making a book by gluing pictures back to back. He put the glue in the center of the pages so the edges were loose. I suggested that he glue the edges together, as well. He didn't understand why it was important, so I asked him to try to "read" his book by turning the pages. He had to turn two edges to see the next page, so he then understood the user experience that needed to improve.
Test, test, test. And catch 'em young, that's what I say.