Today, tablet devices are one of the most important innovations that technology offers to the user. For the fields like communication, social networks, music, games and many more, these devices have created a new media to children's picture books as well. On tablet devices, children's picture books emerge as "applications". Even though book applications hold the concept of the book in terms of content, the form has moved into a totally different environment. By bringing sound, movement, interaction and games to once static and printed pages, these applications present some innovations that might change the way readers read books. Also thanks to these opportunities, book applications not only present the content but also they can provide a rich learning experience. Just like in the print media; developmentally appropriate applications, which are qualified in terms of design and content need to arise. Making a design for children on tablet devices bring about many questions. Factors that should be considered are both differentiated and similar from place to place in comparison with a traditional children's book. Within the frame of descriptive method, this study examines that "how a qualified children's book application should be in terms of form and content" by scrutinizing design principles in this area.