Number books are an effective tool to increase math talk and promote children's mathematical thinking, but little is known about book genre effects. How do different types of number books impact mathematical input? This study examined whether book genre affects the amount and types of teachers' math talk. Using a within-subjects design, we asked 31 teachers of 4- to 5-year-olds to read a narrative number book and a nonnarrative number book in a counterbalanced order. The books were matched in target numerical content. We found that the nonnarrative number book elicited more math talk than the narrative number book. In a qualitative analysis, we analyzed multiple conversational turns and found that both books allowed teachers to engage in simple math discussions, but there were differences in other types of math discussions. Together, these findings show that the quantity and quality of mathematical input differ as a function of genre.