Something Borrowed: A Novel / Emily Giffin,

Rachel White is the consummate good girl. A hard-working attorney at a large Manhattan law firm and a diligent maid of honor to her charmed best friend Darcy, Rachel has always played by all the rules. Since grade school, she has watched Darcy shine, quietly accepting the sidekick role in their lopsided friendship.

But that suddenly changes the night of her thirtieth birthday when Rachel finally confesses her feelings to Darcy's fiance, and is both horrified and thrilled to discover that he feels the same way. As the wedding date draws near, events spiral out of control, and Rachel knows she must make a choice between her heart and conscience. In so doing, she discovers that the lines between right and wrong can be blurry, endings aren't always neat, and sometimes you have to risk everything to be true to yourself.

The smash-hit debut novel for every woman who has ever had a complicated love-hate friendship.