There’s a particular kind of chaos that only an outsider can cause in a friend group that’s been sealed shut since middle school, and Jenny Jackson spends all of “The Shampoo Effect” gleefully cracking that seal open.
Caroline Lash, a Manhattan editor burned out on her career and her mother’s expectations, decamps to the fictional Massachusetts beach town of Greenhead for an eighteen-month writing fellowship. She falls for Van Whittaker, an environmental scientist so wholesomely devoted to his hometown’s dunes that he doubles as the novel’s walking metaphor for preservation. Van comes bundled with a lifelong crew of friends who’ve known each other since they were swapping pajama stories at sleepovers, and who revert to their teenage selves the instant they’re all in a room together. The idyll cracks when Bailey, Van’s on-and-off situationship, reveals she’s pregnant with his child just as he and Caroline are falling in love. What follows isn’t really a love triangle so much as a slow-motion excavation of everything this group has spent years quietly agreeing not to say out loud.
Jackson, who also wrote the bestselling “Pineapple Street,” has a real gift for making wealthy, insular people entertaining rather than insufferable, and “The Shampoo Effect” leans hard into that skill. The dialogue crackles with the specific shorthand of people who’ve known each other since childhood — the kind of friends who don’t ask “what are you doing later,” they just show up in your driveway. Caroline’s outsider perspective gives Jackson license to needle the group’s insularity without ever losing affection for them, and the novel’s funniest scenes are the ones where Van, reliably capable and considerate on his own, dissolves into his least mature self the second his childhood friends are within earshot. Underneath the beach-read packaging, Jackson is doing something sharper: tracking how a baby born outside the marriage scrambles every adult relationship in its orbit, not just the two people involved.
Early coverage has largely framed the novel as an update of John Updike’s suburban infidelity classics for a millennial, more self-aware generation — funny and breezy on the surface, but genuinely interested in how motherhood, long friendship, and forgiveness get complicated once people stop being able to control their own timelines. Reviewers have been especially taken with how unsentimental the book is about friendship itself: these are bonds the characters have to actively maintain, not automatic loyalty the way family is often treated, and several critics singled out that tension as the novel’s most interesting idea. Commentary has been warm rather than rapturous, with most quibbles centered on pacing in the back third, once the central pregnancy reveal has done its narrative work and the story shifts into cleanup mode.
“The Shampoo Effect” earns its place on the beach-read shelf without coasting on the genre’s lower expectations. It’s funniest when it’s meanest, and Jackson never lets the humor undercut how seriously she takes the mess of adult friendship — the debts, the resentments, the sheer work of staying close to people who knew you before you became yourself. Readers who loved “Pineapple Street” will recognize the same sly generosity toward flawed, comfortable people, applied here to an even more universal subject: the friends who never quite let you grow up around them.
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