Purple And Black by K.J. Parker

Set in a world of political intrigue and warfare, this epistolary novel unfolds through a series of letters between two former university friends, one now an emperor and the other a provincial governor. As they navigate the complexities of ruling an empire on the brink of collapse, their correspondence reveals the personal and political challenges they face, including betrayal, loyalty, and the burdens of leadership. The narrative explores themes of friendship, power, and the moral dilemmas inherent in governance, all set against the backdrop of a crumbling empire and the haunting specter of civil war.