Improving reading instruction is one of the hottest topics in K-12 education today. It is also one of the most complex, encompassing pedagogy, policy, and politics -- all rooted in a long history of arguments about the best way to teach kids to read. This analysis is a primer on the "Science of Reading" and efforts to implement it across the country, designed primarily to inform policymakers, advocates, and members of the news media. The goal for this report is to provide a clear fact base for discussions about reading instruction, state-level policies governing it, and relevant lessons from past large-scale reform efforts. The authors hope it serves as a resource for stakeholders as they navigate reading policy in their own contexts.