This study aimed to examine the influence of the complexity of the storybook on caregiver extratextual talk (i.e., interactions beyond text reading) during shared reading with preschool-age children. Fifty-three mother-child dyads (3;00–4;11) were video-recorded sharing two ostensibly similar picturebooks: a simple story (containing no false belief) and a complex story (containing a false belief central to the plot, which provided content that was more challenging for preschoolers to understand). Book-reading interactions were transcribed and coded. Results showed that the complex stories facilitated more extratextual talk from mothers, and a higher quality of extratextual talk (as indexed by linguistic richness and level of abstraction). Although the type of story did not affect the number of questions mothers posed, more elaborative follow ups on children’s responses were provided by mothers when sharing complex stories. Complex stories may facilitate more and linguistically richer caregiver extratextual talk, having implications for preschoolers’ developing language abilities.