This book is by the author of the Sisterhood of Traveling Pants ones, but geared more towards adults. I wish I would of read it in the summer since it takes place largely in a beach community, which btw I love. I always wanted the summer cabin on the lake you went to as a teen. Now my parents did finally buy a cabin, but I ended up being married when that happened and it's in the forest, 20 minutes from any lakeshore, lol.
Anyways, the book is about 2 sisters and 1 friend and no, it's not that both sisters are in love with him. It does have a lot to do with the loyalty of sisters, best friends, and how some people grow up and some don't. It's not the deepest book I ever read and is more on the sad side, but I did like it a lot and would recommend it.