Themes that are relatable to their little lives are a must. A book about going to the park or having a tea party, things that preschoolers might do in their daily lives, can make them feel like they are part of the story. Such as in 'The Little Mouse, The Red Ripe Strawberry, and The Big Hungry Bear', the idea of protecting a strawberry is something they can understand and put themselves in the mouse's shoes.
Simple and repetitive language is important. In books like 'Brown Bear, Brown Bear, What Do You See?', the repetitive pattern helps preschoolers follow along easily and get immersed in the story. They can start to anticipate what comes next and feel more involved.