Procopius--The Secret History of the Courts of Justinian a.k.a. The Secret History second only to Suetonius in gossipy vitriol, this history of the the Court helps us to better appreciate the derogatory adjective "byzantine."
John Webster--The White Devil Read it to truly appreciate the greatness of Shakespeare, but also for its sheer lurid awfulness--not in prose or poetry but in story conception.