What is the main conflict in The Vampire Diaries: The Awakening and the Struggle by L.J. Smith?

The first two books (The Awakening & The Struggle) are collected into the first volume of The Vampire Diaries by L.J. Smith, and form the first part of an ongoing series of vampire romance. Set in the fictional town of Fells Church, somewhere in modern North America, we find our protagonist Elena Gilbert, a teenage girl just about to attend her last year at Robert E Lee High School when she becomes entranced by the mysterious newcomer Stefan Salvatore. What ensues is a dark romance between the two protagonists as Elena Gilbert discovers that Stefan is in fact a centuries old vampire, who is locked into a terrifying feud with his older brother Damon.