There are limited studies with conflicting results examining textbook use and student performance at the university level. To learn more, we surveyed instructors and over one thousand students in 12 undergraduate introductory science courses. The majority (77%) of the students reported reading the textbook either "often" (>75% of the assigned reading) or "sometimes" (25%-75% of the assigned reading). Those who read "often" had better final marks those who read "sometimes," but surprisingly, those who reported "rarely" reading the textbook did as well as those who read "often." Perceptions of the usefulness of the textbook were generally more favorable in courses in which some marks were based solely on the readings. We conclude that there appears to be different types of learners: some may need to read the textbook "often" to do well, while others do not.