The cover of a children's book could play a crucial role in attracting the attention of young readers and influencing their decision to pick up and read the book. In this study, we aim to identify the factors that contribute to the appeal of children's book covers. Given that the target audience for children's books changes as children grow older, we divide our analysis into five age groups. We conduct a series of experiments in which we analyze three distinct aspects of covers: the visual attributes, visible objects, and implied story. Our results show that visual attributes play an important role in determining the appeal of a book. We also find that objects and themes present on a book cover vary between age groups. By understanding the elements that contribute to the appeal of children's book covers, we hope to improve recommendations for young readers and encourage a lifelong love of reading.