This paper provides results from the randomized control trial project, Promoting Development and Home Reading of Supplementary Texts for Young Readers in Cambodia. One control and three treatment groups were assessed on how literacy and reading habits changed when households were provided a variety of high-quality and low-cost early reading materials along with varying degrees of encouragement toward building better reading habits. The findings show that providing books in isolation was not enough. Rather, books in conjunction with a network of reading supports was found to be an effective means to boost reading outcomes, including reading proficiency measures, frequency of reading, and attitudes toward reading. The results highlight the need for at-home reading materials in poor households as an integral step to improve early reading. [This paper is a product of the Education Global Practice.]