This Side of Paradise by F. Scott Fitzgerald.

Meet Naomi and Nicholas: the Perfect Couple. Their glorious, lavish wedding is coming up in three short months . . . and they are utterly, miserably sick of each other. Unfortunately, whoever backs out first will end up bearing the brunt of the wedding bill. When Naomi finds out that Nicholas has been feigning contentment too, the two of them go head-to-head in a battle of sabotage, pranks, and all-out emotional warfare to see who can annoy the other into surrendering first. Now that they have nothing to lose, they're finally being themselves. In fact, they're having so much fun getting on each other's nerves that it starts to feel like something else entirely...