Aside Kodiologist's very good suggestions (+1) I would also recommend looking at the subject of observational studies. I think it is very unappreciated field between data-scientists despite the fact that in many cases the data analysed are of observational nature. I think this is because the bulk of bibliography (especially in Biostatistics) assume at least some quasi-experimental design is already in place. Paul Rosenbaum's books Observational Studies and Design of Observational Studies are some of the most commonly used references.