In the summer of 1977, Victoria Leonard’s world changes forever when Caitlin Somers chooses her as a friend. Dazzling, reckless Caitlin welcomes Vix into the heart of her sprawling, eccentric family, opening doors to a world of unimaginable privilege, sweeping her away to vacations on Martha’s Vineyard, an enchanting place where the two friends become “summer sisters”. Now, years later, Vix is working in New York City. Caitlin is getting married on the Vineyard. And the early magic of their long complicated friendship has faded.

Katherine and Michael are in love, and Katherine knows it's forever - especially after she loses her virginity to him. But when they're separated for the summer, she begins to have feelings for another boy. What does this say about her love for Michael? And what does "forever" mean, anyway? Is this the love of a lifetime, or the very beginning of a lifetime of love?

Margo and B.B. are each divorced, and each is trying to reinvent her life in Colorado - while their respective teenage daughters look on with a mixture of humor and horror. But even smart women sometimes have a lot to learn - and they will, when B.B.’s ex-husband moves in next door to Margo.

Margaret Simon, almost 12, has just moved from New York City to the suburbs, and she’s anxious to fit in with her new friends. When she’s asked to join a secret club, she jumps at the chance. But when the girls start talking about boys, bras, and getting their first periods, Margaret starts to wonder if she’s normal. There are some things about growing up that are hard for her to talk about, even with her friends. Lucky for Margaret, she’s got someone else to confide in...someone who always listens.

After being together for 10 years, Sylvie and Dan have all the trimmings of a happy life and marriage; they have a comfortable home, fulfilling jobs, and beautiful twin girls and communicate so seamlessly, they finish each other's sentences. However, a trip to the doctor projects they will live another 68 years together, and panic sets in. They never expected "until death do us part" to mean seven decades. In the name of marriage survival, they quickly concoct a plan to keep their relationship fresh and exciting.