The book sets "Preschool Education Activity Guidebook" for teachers and "Let's Join Hands for Preschool Education" for children have been provided by the Ministry of National Education to all preschool education institutions since 2017 in order to provide high-quality preschool education, to help teachers develop different perspectives, and to discourage both students and teachers from using unreliable or inappropriate sources of information. The aim of this study was to determine the effects of the book sets on teachers and children. Phenomenology, which is qualitative research design, was used. The sample consisted of 24 preschool teachers from different educational institutions. Data were collected using interview forms created in Google Forms. Data were analyzed using second-cycle coding, which is inductive content analysis. Many participants are satisfied with the activity guidebooks and use them to develop different perspectives, to improve themselves, and to be more productive for their students. Teaching experiences and classroom materials affect the way they use the activity guidebooks. Although the book sets have some negative effects, they are guides for both teachers and parents. Participants think that the book sets are useful for education planning and process management but that different variables should also be taken into account when integrating them in education and that all available resources should be used to achieve professional development.