A tale of identical twins and not-so-identical islands.When blue-blooded Boston designer Eleanor Roxie-Frost divorces electrical contractor Billy Frost, the rift consigns their 17-year-old identical twin daughters to separate islands. When they're home from college, Tabitha spends the summers with Eleanor on Nantucket and Harper lives on the Vineyard with Billy, and they visit the opposite parents for holidays. Now the twins are 39 and haven't gotten along in years. For reasons that will remain obscure until the end, Tabitha blames Harper for the death of her premature son, Julian. Neither Tabitha nor Harper has ever married. Tabitha had daughter Ainsley and, later, son Julian out of wedlock with her long-term boyfriend, Wyatt (now married to someone else and effectively out of Ainsley's life). Tabitha, who has lived her entire adult life in Eleanor's thrall, occupies her mother's carriage house and manages the ERF boutique on Nantucket, a stodgy purveyor of preppy resort wear on the verge of going bust. Harper, whose past includes menial jobs and a brush with the law, is now a total pariah on the Vineyard: she'd been having an affair with Billy's doctor, Reed, which is discovered by his wife, Sadie, on the night Billy dies. The fun accelerates when Eleanor, Ainsley (now 16), and Tabitha attend Billy's memorial service only to have Sadie toss a flute of champagne in Tabitha's face. Then Eleanor, who could never handle champagne, breaks a hip. For complicated reasons, the twins end up trading islands, with Tabitha heading to the Vineyard to renovate Billy's house and then sell it while Harper goes to Nantucket to look after her niece. Hilderbrand makes the most of the complications caused by twinship and small island worlds: Tabitha's most recent ex, Ramsay, approaches Harper and decides to pursue this less uptight look-alike, and Tabitha, after some initial difficulties occasioned by Harper's reputation, falls for master builder Franklin—who is Sadie's brother. The most poignant scenes feature Ainsley, whose teen angst is quelled by Harper's nurturing. The romantic relationships seem tacked on to satisfy the demands of the genre, but this beach read doesn't shy from the grittier side of all that sand. Intelligent escapism with heart.