It is commonly believed that reading challenges should be addressed early to reduce the likelihood that developmental delays will impact students over the long term. However, students in developing countries often have limited access to reading resources. In this study, the authors used a randomized controlled trial of 11,083 fourth- and fifth-grade students in 120 primary schools in rural China to examine the causal effect of an in-class library program on student reading outcomes and academic achievement in schools with poor reading resources over an eight-month period. An in-class library was installed in each of the selected classes in the 40 treatment schools. The authors found that the program significantly improved student affinity toward reading and student reading habits, and in these regards, it narrowed the gap between male and female students, between low- and high-performing students, and between left-behind children and children living with parents. However, the authors found no overall effect of the program on reading and academic achievement and a negative effect on student confidence in reading. There was also no effect on student, teacher, and primary caregiver perceptions toward the effect of independent reading on academic achievement, nor any effect on whether teachers and primary caregivers provided reading instructions to students. The authors propose three possible explanations for these findings: a lack of reading instruction from teachers and caregivers, a lack of reading materials specifically tailored to local needs and interests, and the relatively short duration of the intervention.