The Unhoneymooners (Unhoneymooners #1) by Christina Lauren
Summary (from the publisher): Olive is always unlucky: in her career, in love, in…well, everything. Her identical twin sister Ami, on the other hand, is probably the luckiest person in the world. Her meet-cute with her fiancĂ© is something out of a romantic comedy (gag) and she’s managed to finance her entire wedding by winning a series of Internet contests (double gag). Worst of all, she’s forcing Olive to spend the day with her sworn enemy, Ethan, who just happens to be the best man. Olive braces herself to get through 24 hours of wedding hell before she can return to her comfortable, unlucky life. But when the entire wedding party gets food poisoning from eating bad shellfish, the only people who aren’t affected are Olive and Ethan. And now there’s an all-expenses-paid honeymoon in Hawaii up for grabs. Putting their mutual hatred aside for the sake of a free vacation, Olive and Ethan head for paradise, determined to avoid each other at all costs. But when Olive runs into...