Four mismatched girls spend an unforgettable summer together in a funny, heartfelt YA novel for fans of The Sisterhood of the Traveling Pants.    Four girls are forced to spend the summer together when their moms reunite at their childhood lake house. What happens next involves midnight boat rides, flaming marshmallows, sandbar parties, crushes and heartache, and a summer they'll never forget. Always-sunny Skyler is a softball star who's hiding how bad her joint pain has gotten. Always-stormy Scarlett, Skyler's twin, would much rather be hanging out with her boyfriend back home. Amelia Grace just wants to escape her conservative stepdad after he caught her kissing a girl. And homeschooled social-media star Ellie is just excited at the chance to make some friends IRL.   The girls are facing a long few months together, until they find the remnants of a secret society whose rules included playing poker, wearing pearls, telling the truth . . . and accomplishing something impossible by the end of the summer.   "Allen's well-rounded, realistic teen characters grow throughout, and she interlaces the story with complicated relationships that reveal each character's idea of friendship . . . An engaging coming-of-age story." — Kirkus