The Peek-a-Flap Upsize series is a collection of interactive lift-the-flap board books published by Cottage Door Press, designed for babies and toddlers under three years of age. These oversized board books feature chunky, durable pages with thick, reinforced flaps that young children can lift to discover hidden pictures and surprises on every spread. The larger format makes it easier for little hands to grasp and manipulate the flaps, building fine motor skills and hand-eye coordination through play.

Each book in the Peek-a-Flap series is rich with colorful illustrations and age-appropriate content that encourages early vocabulary development, curiosity, and interactive storytelling between caregivers and children. The sturdy construction is designed to withstand the enthusiastic handling typical of infants and toddlers, making these books a durable choice for repeated reading. Sold at Costco in a children's/juvenile classification, this set offers excellent value as a gift or starter library addition for the youngest readers.