Special Prosecutor Robert Meuller's Indictment
It provides detailed chapter and verse on who were the people involved, how the Russians set about their tasks and even identifies some of the tools involved. It is a case study in how to conduct a cyber attack against an adversary. If you are familiar with the "kiil chain" it follows those activities quite closely. For anyone who is engaged in cyber security I recommend that you take time out to read the indictment because it describes an attack playbook.