Leaves
This simple, charming story of a young bear's first autumn is perfectly suited to board book format. Bear is surprised when the leaves start falling off the trees, but when he tries to reattach them, it doesn't work. Eventually, he gets sleepy, and burrows into the fallen leaves for a long nap. When he wakes up, it's spring-and there are suddenly brand-new leaves all around, seeming to welcome him.
With its childlike main character and graceful illustrations, Leaves is a great way to teach the youngest children about the changing seasons.