That Summer by Jennifer Weiner

[Atria] From the #1 New York Times bestselling author of Big Summer and “undisputed boss of the beach read” (The New York Times) comes another timely and deliciously twisty novel of intrigue, secrets, and the transformative power of female friendship. Daisy Shoemaker can’t sleep. With a thriving cooking business, full schedule of volunteer work, and a beautiful home in the Philadelphia suburbs, she should be content. But her teenage daughter can be a handful, her husband can be distant, her work can feel trivial, and she has lots of acquaintances, but no real friends. Still, Daisy knows she’s got it good. So why is she up all night? While Daisy tries to identify the root of her dissatisfaction, she’s also receiving misdirected emails meant for a woman named Diana Starling, whose email address is just one punctuation mark away from her own. While Daisy’s driving carpools, Diana is chairing meetings. While Daisy’s making dinner, Diana’s making plans to reorganize corporations.