For data champions specifically, I agree with the recommendations for Driven by Data (understanding data from a teacher and school leader perspective) and Tufte's books (visualizations). Additional ones are (good reference guides, don't really need to be read front-to-back):
- Methods Matter: Improving Causal Inference in Educational and Social Science Research - research methods for education, basically a textbook
- Stephen Few's books - visualization
- Improving Survey Questions: Design and Evaluation - creating and analyzing surveys
From my experience, it also depends very much on someone's background. Most of our analysts/data champions have come from outside education and encouraged them to read books to give them more context on education in the US. and our students rather than data-related topics.