A few months ago I read Queen Bees & Wannabes, Rosalind Wiseman’s nonfiction book about cliques and the subtleties of teenage girls’ relationships. I was particularly struck by her observation that girls’ friendships with other girls are very frequently as intense, as emotionally complex and important as those they will later have with their boyfriends and lovers. Something Borrowed illustrates the complexity of female friendship from the point of view of the least powerful girl in the relationship, imagining what would happen if she stepped out of that role and did something completely unexpected.

Rachel White has always been the good girl. She’s always made good grades, fulfilled her parents expectations, lived cleanly and neatly and, above all, she’s been a good friend. Her friendship with Darcy Rhone goes back over 25 years when the two of them lived next door to each other in Naperville, Indiana. Darcy, unlike Rachel, is a glamour girl. She’s always been the pretty one, the popular one, the one who could sway public opinion with a single word or gesture. Rachel’s success as an attorney is built on hard work; she pulled lots of all-nighters in law school and landed a job at a big firm in New York. Darcy’s, on the other hand, is pretty much luck. Everyone likes her, she expects to get her way, and somehow she always does. At several critical intervals in their friendship, her gain has been Rachel’s loss.

Still, Rachel’s always sucked it up. After all, they’ve been friends forever, and Darcy is affectionate, outwardly loyal, and fun. If she got the guy Rachel lusted over in law school but knew she was no match for – well, that’s life. Until a few too many drinks at her 30th birthday party leads to Rachel going home with Darcy’s fiancé, Dexter. And then suddenly, Rachel must examine her loyalties. Which is more important – love or friendship?

Though the conflict in Something Borrowed hinges on a romantic relationship, this is not a romance. Dex is definitely a secondary character. Most of the story, told from Rachel’s first-person-point of view, is about a flawed friendship and how Darcy’s long list of smaller betrayals lead to Rachel’s being able to commit the ultimate one. While this is not an adultery book, as Darcy and Dex are only engaged to be married, there is no doubt that, for most readers, sleeping with your best friend’s fiancé is a line-crossing action. Rachel is Darcy’s maid of honor, after all. She is helping Darcy plan her wedding – and then calling Dex on her cell phone to schedule evening rendezvous. Can a heroine still be a “heroine” when she is doing something so selfish and backstabbing?

Ultimately I think Giffin succeeded in writing Rachel as a flawed but still likable character. Part of this is because so much of the book is Rachel’s self-flagellating interior monologue. While she continues to betray Darcy, Rachel does not flinch in examining her own motivations. She does occasionally rationalize, but she doesn’t let herself off the moral hook. She knows what she is doing is wrong, and she regrets it. But her relationship with Darcy is more like a failed marriage than a mutually supportive friendship. She stays with Darcy because she’s always been with Darcy, not because the friendship continues to offer her anything substantial. For Darcy, it’s worthwhile because Rachel is passive and giving. She forgives Darcy’s unsubtle criticisms and selfishness and is always there to give her moral support in a crisis. Everyone, especially friends and family back in Indiana, thinks of Darcy and Rachel as an institution. Always together. So how does a passive person get out of a bad relationship? She cheats. That she gets the guy she’s always wanted is just killing two birds with one stone.

The fact that Darcy is so shallow, so selfish, and so childish also makes the idea of her marriage to Dex, Mr. Straight-up, very unpalatable. It’s impossible for anyone to want a couple this mismatched to actually walk down the aisle and say vows. The hard part is understanding how they stayed together for seven years and what made Dex propose in the first place.

It is much easier to see what he admires about Rachel. She’s smart and capable, yet also kind and down-to-earth. Partying with Darcy in the Big City hasn’t shaken free her Midwestern values. She knows what really matters. And she and Dex have a great deal in common. They both think like lawyers; this is one book in which the characters’ careers don’t feel tacked on. Rachel actually mentally defends her cheating in legalese which makes for an interesting take on the matter.

Rachel’s passivity is somewhat aggravating to read about, however. She refuses to set real boundaries with Darcy that would equalize their relationship. She works a job she hates rather than muster up the energy to find something she would really love. Her love life, even with Dexter, has been a series of falling into relationships rather than seeking them out or going after them. And she is reluctant to be straight with Rachel about her affair with Dexter or let Dex know what she expects to come of any of this. She prefers to let it all sort itself out rather than take responsibility for making anything happen.

Something Borrowed is smoothly written. Giffin’s dialogue is especially good, and her secondary characters are well drawn. Ultimately it was the unusual conflict that kept me reading up all night, however. I wanted to know how a nice girl could do something so dishonest and how the whole mess would shake out. Giffin’s follow-up book, Something Blue, published last month, is written from Darcy’s point of view, and I’m interested in seeing how Darcy shakes out as a heroine and whether Rachel and Darcy will ever be friends again. I’ll be reading that one very soon and looking for more from Giffin in the future.