Bloom by Sarah Blynne
Set during the 2006-2007 school year, seventeen-year-old Seth Harris is a lazy and angry high school senior who would rather spend his time writing than doing actual schoolwork. When he unexpectedly meets an equally unmotivated and rebellious Tessa Copeland and starts dating her, he has one goal: not to give up on his relationship, like his mother did to his father.
That becomes easier said than done when he meets Marie Burn, a fellow writer, studious student, and a bubbly person. When he becomes closer to Marie, everything he was sure of is called into question. As Seth continues to deny his changing feelings, he has to make a choice between keeping his promise of loyalty to Tessa, or accept what his heart really wants and feels.