This charming coming-of-age novel becomes, over time, a paean to a mother’s love and the treacherous territory of childraising post-divorce. Miles Alder-Rich has nothing in mind but the usual nine-year-old boy’s curiosity about what his parents say about him behind closed doors. He doesn’t want to hear their bedroom secrets, only discussions that relate to his own interests. Abetted by his best friend, Hector, the two improvise a walkie-talkie to listen in on private conversations, a successful gambit that morphs into more sophisticated methods to overhear telephone conversations.

Miles is abruptly pulled from his childish concerns when he hears his mother, Irene, talking about a divorce with her best friend. All too soon his fears become a reality, and Miles faces the prospect of life in a bifurcated California home. Still, relations with his father remain friendly, his parents managing a wonderful friendship even after their separation, the children never experiencing the abandonment of a father.

Everything Miles learns as time goes by is due to his eavesdropping, all of which he shares with Hector, who soon finds himself in a similar situation. Eventually Miles realizes that his mother is attracted to a man who works on another coast. Eli Lee moves slowly into the family circle (Miles and his younger twin sisters, Boop One and Boop Two), conscious of Irene’s concerns and her fear of making a mistake. Nothing like the children’s father—Cary, an entertainment lawyer—Eli is fascinated by Irene’s work as a mathematician.

What makes Simpson’s book so charming is the natural demeanor of her characters, especially the narrator as he evolves from self-obsessed child to concerned young son looking out for his mother’s best interests. His exchanges with Hector, with his mom—whom he calls “the Mims”— and even “the Boops” are as familiar as his California childhood, where sunshine is taken for granted and a big house affords plenty of room to get into mischief. Given Irene’s skills, the language of mathematics is a household staple, at once a comfort and a definition of Irene’s temperate approach to life. (For instance, Miles knows Irene isn’t beautiful, but he is aware of moments when her face is alight with beauty.) Of course, there’s always a serpent in paradise, and Miles comes face to face with the harsh realities of lower incomes and downsized households common to children of divorces. Inhabiting a smaller, rented, home, Miles and Hector fear the worst betrayal of all—that Eli isn’t who he seems.

To that end, the boys engage in more concentrated sleuthing, Miles snooping through his mother’s private papers for clues about the relationship with Eli, who seems to be absent as much as he is present. Growing into adolescence, Miles is gradually shedding his innocence, more vigilant, more aware of his mother’s feelings and concerns. Irene cannot be faulted for any of her decisions, except perhaps an excess of trust in Eli. Subtly, Simpson taps into that particular bond between mothers and sons, a young man developing empathy for the female of the species as modeled by a mother who puts the welfare of her family first. When fate strikes, it delivers a blow that devastates not only Irene but also Miles, who is acutely aware of the delicate territory he has stumbled upon.

There’s nothing epic about this novel. Just a small slice-of-life, it is both heartwarming and honest, a precise rendering of an idyllic childhood in California shattered by curiosity but enriched by the lessons gleaned from his parents’ continued rapport and his mother’s determination to make her children’s lives rich and full regardless of circumstances. That she makes a mistake—and pays for her naiveté dearly—is part of the human story that the author so beautifully portrays.