Best-selling author Jennifer Weiner returns with her fifth novel, Best Friends Forever (2009). Readers meet Addie and Valerie who were once best friends in high school but let a boy come between them (and not in the way readers might at first think). On the night of their high school reunion, Valerie shows up at Addie's front door after not having seen her in years. Disheveled, with blood on her coat and an odd look on her face, Valerie is clearly in trouble and Addie feels an obligation to help her old friend.

As the reunion comes to a close, Valerie has exacted revenge on her high school boyfriend—the same boy who raped her—by making him strip and then stealing his clothes. In her hurry to drive away, she accidentally hits him and is unsure if she has killed him. Addie commits to helping her old friend by aiding and abetting her and the pair revisits their history.

Addie, overweight and unpopular, found the only friend of her childhood in Valerie who was new to the neighborhood. Intrigued by Valerie's mother's spontaneity and fun-loving nature, Addie envies the freedom Valerie has as a child. Valerie, on the other hand, covets the family stability and structure inherent in Addie's life. As Valerie realizes her potential as a beautiful and popular girl in high school, Addie grows full of resentment and jealousy. Despite her treatment of Addie, Valerie confides in her that she has been raped. Addie tells her parents and suffers revenge at the hands of her unforgiving classmates. Ultimately, Addie finishes out her high school years as a pariah. In college, her social life fared no better since her mother became ill and Addie had to drop out to care for her.

Now a greeting-card artist, Addie remains somewhat of a recluse in the house she grew up in. She is also saddled with the responsibility of caring for her brain damaged brother, who resides in a nearby facility. Valerie's unexpected appearance not only provides her with a chance to rekindle a long lost friendship, but also introduces her to a man who may prove to be part of her future.

As the girls' adventure unfolds, they come to terms with the events that drove them apart so many years ago while opening the door for a renewed future friendship.