New Yorker Molly Blum knows everything about her lifelong nemesis, Jude Stark. With their families so close, they should have been best friends. Instead, she thinks he's a too-charming slacker, and he thinks she's allergic to fun. After years of one-upping each other's pranks (chocolate-dipped cat treats are not as delicious as they appear), one high school joke went too far, and they stopped speaking completely. But now that they're supposed to help plan a massive party for their parents-together-there's no better time to resume their war.

And it is on. Only somewhere between all the sniping and harmless hijinks, a reluctant friendship develops, along with an unexpected spark of sexual tension. It might have to do with the fact that she's been dating Jude-lookalikes and he's been dating Molly doppelgangers. Or the fact that neither of them is nearly as horrible as they thought. All Molly and Jude know is that they've mastered the art of hating each other. Falling in love, on the other hand, is a whole new battlefield.