
The first class I read this with was a kindergarten class and I thought that I might have to explain it a bit to them. Wrong. They explained it to me. I didn't notice that the first page has an apple tree and the last page has a pear tree. When they wake from their nap they aren't in the same spot. There's actually quite a few differences between the first and last pages.
Sam and Dave Dig a Hole is a book of few words and really quite simple but the illustrations by Jon Klassen certainly make the story as good as it is.