This study examines the influence of reading and planning from two differently organized mathematics textbooks on prospective high school mathematics teachers' pedagogical content knowledge and content knowledge of exponential functions. The teachers completed a pretest and two posttests. On the pretest, the teachers possessed an incomplete understanding of content and pedagogical content knowledge related to exponential functions. The teachers' understanding of how to translate from table to closed-form and recursive equations grew as a result of their use of the "Mathematics: Modeling Our World" textbook, while the "Discovering Algebra" textbook appeared to be more beneficial in terms of pedagogical content knowledge. Teachers read from the student lessons in both textbooks, but read differently from the sections of both textbooks intended for the teacher. They focused more on the purpose of the "Mathematics: Modeling Our World" lesson and more on the places where students might experience difficulties in the margins of the "Discovering Algebra" lesson. The teachers' learning was influenced by their own personal characteristics (e.g., previous textbook experiences) as well as textbook qualities (e.g., organization).