Have you read the story Brown Bear, Brown Bear, What Do You See? to a child? It's a repetitive story written by Bill Martin Jr. and illustrated by Eric Carle. Children love this story read to them over and over. It's so good for their little brains. Each page asks the question, "Brown Bear, Brown Bear, What do you see? A child listening to the story gets to try to remember what the Brown Bear sees next before the page is turned.
Eric Carle reads this story aloud at this link.
My oldest son "reads" this story by memory at the age of two, because he loved it and made me read it to him about 100 times. Here's a video of my son "reading" this book. (Sorry about the noise in the background. We had the window open, and cars were driving by.)
Board books are great for children under four years of age. Here's a great set of board books that includes Brown Bear, Brown Bear, What Do You See?