From the author of My Life Next Door comes a swoony summertime romance full of expectation and regret, humor and hard questions. Gwen Castle's Biggest Mistake Ever, Cassidy Somers, is slumming it as a yard boy on her Nantucket-esque island this summer. He's a rich kid from across the bridge in Stony Bay, and she hails from a family of fishermen and housecleaners who keep the island's summer peo...