The Vampire Diaries: Stefan's Diaries #1: Origins

Set during the Civil War, against a backdrop of grand estates, unimaginable riches, and deadly secrets, three teenagers in Mystic Falls, Virginia enter a torrid love triangle that will span eternity.
Brothers Stefan and Damon Salvatore are inseparable until they meet Katherine, a stunning, mysterious woman who turns their world upside down. Siblings turned rivals, the Salvatores compete for Katherine's affection, only to discover that her sumptuous silk dresses and glittering gems hide a terrible secret: Katherine is a vampire. And she is intent on turning them into vampires so they can live together-forever.
Based on the popular CW TV show inspired by the bestselling novels, Stefan's Diaries reveals the truth about what really happened between Stefan, Damon, and Katherine—and how the Vampire Diaries love triangle began.