The aim of this study was to investigate the effects of personalized books on parents' and children's engagement during shared book reading. Seven native English parents and their children aged between 12 and 33 months were observed at home when sharing a book made specifically for the child (i.e. a personalized book), a comparable book with no personalized content, and a favourite book of the child. The interactions were videotaped and later coded to provide information about the frequency of behaviours that indicated engagement with the books. Statistical analyses revealed that children and parents showed significantly higher overall frequencies of smiles and laughs with the personalized books in comparison to the non-personalized books, and showed higher frequency of vocal activity with the personalized as opposed to the child's favourite book. In addition, there was a significantly higher rate of children's smiles and laughs with the personalized than with the non-personalized book. It appeared that most of the children's positive affect with the personalized books was in response to the content of those books, while the parents' smiles occurred mostly in response to a smile or laugh from the child. These findings are among the first to suggest that personalized features of books result in specific distinct responses in parents and children during shared book reading.