An accidental pregnancy turns a tight-knit group on its head in this witty and irresistible summer novel from the New York Times bestselling author. Perfect for fans of Curtis Sittenfeld, Alison Espach and Catherine Newman. THE NEW YORK TIMES BESTSELLERA READ WITH JENNA BOOK CLUB PICKA VOGUE 'BEST BOOK OF 2026'‘Funny, drama-fuelled, and full of Jackson's breezy wit…Brilliant’ COCO MELLORS, Sunday Times bestselling author of BLUE SISTERS'The platonic ideal of a beach read: fun and fast-paced'New York Times'An absolute DELIGHT . . . a must, must, must for your summer reading list'ELIN HILDERBRAND, New York Times bestselling author of THE FIVE STAR WEEKENDOVER ONE LONG SUMMER, WHO KNOWS WHAT MIGHT COME OUT IN THE WASH?When writer Caroline Lash arrives in Greenhead, she falls immediately for its scenic beaches and New England charm – and even harder for Van Whittaker, a gorgeous, fleece-wearing, litter-collecting, kayak enthusiast. She meets his friends: Augusta, old money and uptight; Fran, drowning in everyone else’s problems whilst keeping two kids (and an inebriated husband) afloat; and Bailey, who is sexy, confident… and inconveniently pregnant with Van’s child. Determined nothing will dull the shine of her new romance, Caroline joins the friends as they run wild through Greenhead, drinking on houseboats, gossiping on beaches while their children paddle, and playing risky games. It seems the fun will last forever – until it doesn’t. As decades-old friendships and marriages begin to fracture, Caroline’s place in their world is called into question. And with all the group’s most tightly held secrets at stake, who knows what might come out?Dazzlingly funny, sexy, and as juicy as it is astute, The Shampoo Effect is a story of late-night parties, early mornings with small children, and old friends finally growing up – despite all their best efforts. Praise for The Shampoo Effect:'So breezily readable and laugh-out-loud funny' CATHERINE NEWMAN, bestselling author of WE ALL WANT IMPOSSIBLE THINGS‘The perfect smart summer book.’ DAISY BUCHANAN, author of CAREERING'Funny, sharp and charming'REBECCA SERLE, New York Times bestselling author of IN FIVE YEARS‘A delicious, unputdownable portrait of a group of friends navigating love, marriage, and young parenthood…I loved it.’BELLE BURDEN, bestselling author of STRANGERS‘Smart, funny, and perceptive…an addictive, beautifully observed read.’LOUISE O’NEILL, bestselling author of IDOLReaders LOVE The Shampoo Effect:'I can't tell you how much I loved being inside the pages of this book.' 5* reader review'The perfect beachy, summery read; it's messy, dramatic, funny, and completely entertaining.' 5* reader review'Another great book from Jenny Jackson. ... A very witty and sometimes emotional read.' 5* reader review'All I want in a great character driven novel. Loved it!' 5* reader review'A new favourite book for me.' 5* reader review