This keynote will summarize the results of two randomized studies that provided free self-selected books in an Annual Book Fair format to primary grade children for summer reading. The original study in Florida found that children who received books improved scores on the 3rd grade state high stakes test. The second study in Tennessee--just completed-- also found that children who received free self-selected books obtained significantly higher scores on the 3rd and 4th grade TCAP. Explanations for these results will be explored, including motivation research that privileges interesting texts, topics of personal interest, choice, and peer sharing, as well as the linguistic and cultural properties of the curated corpus of book fair books from which children chose those they wanted to keep. Cost-benefit implications for policy will be discussed.