Absolutely And Forever by Rose Tremain

In early 1960s England, a clever schoolgirl is swept into an all-consuming first love with a charismatic older boy whose evasions and eventual disappearance leave a wound that shapes the course of her life. Across the years—through study, marriage, work, and motherhood—she tests every choice against that first, intoxicating ideal until a late reckoning with the past reveals difficult truths and opens a path to a more honest kind of happiness.