In her tensely constructed and absorbing new novel, “Little Monsters,” Adrienne Brodeur examines dark confidences between parents, children, and siblings. Through the lens of one New England patriarch and his descendants, she asks readers to consider what constitutes a secret, and why families keep them.

The Gardners are blue bloods. Their lives on Cape Cod are filled with conflict and longing, but no one here is struggling to survive. A major point of tension between brother and sister Ken and Abby is the inheritance of a coastal home and art studio that — in true New England patrician style — has its own name, the Arcadia. The siblings are presented as diametrical opposites — he’s a real estate tycoon, and she’s a celebrated visual artist — but their shared knowledge of their childhood unhappiness haunts them.

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The people surrounding Abby and Ken have their own stakes in the intricacies of this family, and their own secrets, too. Their father, Adam, is a renowned oceanographer with bipolar disorder. Ken’s wife, who is also Abby’s best college friend, self-medicates with Sancerre to manage the responsibilities of her own children, her husband’s political aspirations, and the award-winning azaleas in her perfectly kept garden. In the summer of 2016, a mysterious woman noses into each of their lives, and it’s soon clear that she holds the power to fully destabilize the Gardners’ citadel, like a sand castle crumbling under the force of the incoming tide.

It’s a juicy story. Brodeur’s engaging portrait of this family is aided by her facility at dropping in and out of the voices of her sharply discerned characters. The book is told in alternating chapters from the perspectives of five narrators. Adam’s inner monologue edges toward chaos when he decides to forgo his lithium prescription. And Ken’s grandiosity and obliviousness are sharply rendered in his dialogue and the details of the life he lives. Even the tangential players — those who don’t rise to the status of co-narrator — are expertly inhabited. Ken’s twin 12-year-olds are especially well-realized as they insert their Gen Z sensibilities into the political landscape of that pre-Trump summer and the equally fraught family landscape.

Anyone who has taken a family trip to one of America’s coastal vacationlands will recognize the milieu: the unrelenting beauty of the seaside, oafish tourists in the high season, a corner bar the locals visit for a generous pour and fried calamari. Brodeur has indeed crafted a consummate summer read with “Little Monsters,” which somehow evokes smooth beach glass and hot pink sunsets with nary a mention of either. At the same time, she’s added notes of appealing complexity with a labyrinthine sibling relationship that recalls famous literary siblings like Franny and Zooey Glass or the sisters in Marilynne Robinson’s “Housekeeping.”

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As in those earlier works, it’s not always clear in Brodeur’s novel that anyone other than the siblings can grasp what they’ve experienced together and why they hold such deep and affectionate grudges. Just as readers are trying to determine what drives the unspoken mix of anger and love between Ken and Abby, one of Ken’s daughters asks, “What is the deal with you and Dad, Aunt Abby? Like, really, what’s the actual deal?”

“Little Monsters” is a follow up to Brodeur’s successful 2019 memoir, “Wild Game,” about her mother’s infidelity and subsequent decision to make her daughter — the author — complicit in that secret. Also set on Cape Cod and also about a dysfunctional family’s reckoning, “Wild Game” is a nonstop parade of I can’t believe this moments whose power is partly derived from the fact that those moments really happened. “Little Monsters” is fiction, so the stakes are less pronounced, but the peril and betrayal are deeply felt.

In dozens of small moments in the novel, the Gardners brush against our anxious American political situation. Ken is a wealthy, right-leaning businessman, but he can’t deny that the erosion of his property line due to climate change is a real bummer. Adam is a lifelong womanizer confounded by the #MeToo movement who wonders to himself, “When had it become a crime to appreciate an attractive woman?” Abby is a single, professionally successful woman who has to negotiate for her independence, even as a highly qualified woman is running for president and being second-guessed at every step. What’s remarkable about this subtle evocation of our final pre-Trump summer is that it’s as unremarkable to the Gardners as it was to most Americans. We had no idea what was coming, and in this novel, neither do they.

Ultimately, though, the true crisis here is interpersonal rather than sociopolitical. As the novel builds toward its conclusion, Adam’s 70th birthday celebration promises to be the scene where many of this family’s secrets are revealed. Abby has created a painting as a gift for her father, and the canvas’s subject speaks directly to the sources of tension that have locked her and her brother into their elaborate and painful knot all these years. Readers with families like mine will understand why, in all the decades of their relationship, the Gardners didn’t simply speak about their secrets and clear the air. Some situations simply require silence. There are matters so ghastly, so tender, so hard to pin down, and so painfully private that they spawn a work of art. Like a painting. Or a novel.