The young couple Elaine Walker (Frances O'Connor) and the history teacher David Walker (Simon Baker) meets a fifteen years old lonely teenager Chet Becker (Gregory Smith) in an ice-cream shop and they become friends. David has a crush on Elaine and they have one night stand Elaine tells her infidelity to David, and their life is affected by the affair.

"When does one know when a marriage is over? Can a relationship survive the murky waters of infidelity? When do two people realise that they're no longer in love? These are the questions posed in a Book of Love, a smart, perceptive, and engrossing domestic drama that features three of the most astonishingly naturalistic and nuanced performances in recent years.

Book of Love focuses on the tiny stories, the little moments in life where an expression or an action can have enormous and profound significance, whether it's a sight of a fifteen-year-old's swim-toned abs as he pulls of a sweatshirt, a young, impressionable student staring wide-eyed at her teacher, or the look of longing on a woman's face as she ponders committing adultery while her husband sleeps in a hammock in the back yard."