"The Lives of the Twelve Caesars, Volume 04: Caligula" is a historical biography written by C. Suetonius Tranquillus, offering an in-depth account of the life and reign of the Roman Emperor Caligula. The book portrays Caligula's rise to power, his early popularity, and subsequent descent into madness and tyranny. Suetonius explores Caligula's extravagant lifestyle, his alleged sexual perversions, and his acts of cruelty and excess. The biography delves into the emperor's relationships with his family, his political decisions, and the conspiracies that surrounded his rule.