One side is for birth to 3 months -- with high-contrast black, white & red illustrations for early visual stimulation -- the other for 3 to 6 months with brightly colored, more complex 3-D figures and activities, to entice baby to tummy-time play. 
 

The highly contrasting, strong-color (black, white & red) illustrations on one side, and the more complex, more colorful illustrations on the other side, accompany baby as his sense of sight develops over the first few months of his life.
The illustrations are inviting, helping his sense of sight to develop and mature. 

By placing the Double-Sided First Book in front of baby in the prone position, he raises his head to gaze at the illustrations. This helps strengthen the neck and shoulder girdle.