The Wall in the Middle of the Book - Jon Agee

A little knight is very happy that his wall protects him from the dangers that are sure to lurk on the other side. However, he is too busy mending a hole in his wall to notice the mounting dangers on his own side. Luckily he is rescued by one of the baddies on the other side, and finds out that the other side of the wall is actually a much pleasanter place to be.