The Lives of the Twelve Caesars by Suetonius is often seen primarily as a source of gossipy anecdotes, something its author was well-placed to provide thanks to his position at the imperial court and access to its archives. Yet as Mary Beard argues, his work read as a whole, from the rise of Julius Caesar to the reign of Domitian, has important things to say about the transmission of political power.
Free online texts
Gutenburg: The Lives of the Twelve Caesars, translated by Alexander Thomson. Multiple Formats.
Loebulus. L031 - Suetonius -- Suetonius I: Julius. Augustus. Tiberius. Gaius. Caligula. PDF of public domain Loeb edition in Latin and English.
Loebulus. L038 - Suetonius -- Suetonius II: Claudius. Nero. Galba, Otho, and Vitellius. Vespasian. Titus, Domitian. Lives of Illustrious Men: Grammarians and Rhetoricians. Poets (Terence. Virgil. Horace. Tibullus. Persius. Lucan). Lives of Pliny the Elder and Passienus Crispus. PDF of public domain Loeb edition in Latin and English.
Poetry in Translation: The Twelve Caesars, translated by A.S. Kline (2010). multiple formats.
Wikisource: The Lives of the Twelve Caesars.
A Don's Life: Taking Suetonius Seriously, a short blogpost by classicist Mary Beard.
Librivox: The Lives of the Twelve Caesars - public domain audiobook.