The Glimpses Of The Moon by Edith Wharton
Set in the 1920s, The Glimpses of the Moon details the romantic misadventures of Nick Lansing and Susy Branch, a couple with the right connections but not much in the way of funds. They devise a shrewd bargain: they'll marry and spend a year or so sponging off their wealthy friends, honeymooning in their mansions and villas. As Susy explains, "We should really, in a way, help more than hamper each other. We both know the ropes so well; what one of us didn't see the other might - in the way of opportunities, I mean." The other part of the plan states that if either one of them meets someone who can advance them socially, they're each free to dissolve the marriage. How their plan unfolds is a comedy of eros that will charm all fans of Wharton's work.