Lionel Shriver explores just this notion in her extraordinary novel The Post-Birthday World, which also compares two relationships, one broken by infidelity and one not. Only this time, the relationships are one and the same. Shriver alternates, chapter by chapter, between the life of Irina McGovern, who forgoes an affair in an effort to protect her nine-year relationship; and Irina McGovern, who surrenders to an affair, thereby destroying her nine-year relationship. By offering these two fates, Shriver proposes something radical: It's a toss-up. Have an affair, or don't. You'll eventually find yourself making the everyday trudge of intimacy either way.
"Maybe this was what it was like, getting older. You tired of sex, even of good sex, the way you'd tire of a good spaghetti carbonara if you ate it three times a week," Irina-the-faithful thinks." Or maybe there was such a thing as sexual laziness.... In most regards she was industrious; she never purchased precut carrots. But ecstasy, too, was an effort."
On the other hand, Irina-the-cheater also finds that contentment eludes her. "In walking out on [her partner] she had unwittingly repudiated the steady-as-she-goes," she thinks after trying—and failing—to create a comforting dinner routine with her new lover, "and for the moment she was undecided as to whether swapping the glassy waters of popcorn-and-TV for the stormy swoop, lurch and plummet of these last seven months was a criminal swindle or the biggest bargain of her thrifty life." (Which also points to equations that both books put forth: Emotional Struggle = Eroticism; Domesticity = Boring Sex.)
Infidelity, in these stories and, I suppose, in life too, is like walking a tightrope to another version of yourself—someone less burdened, less aged—but once you come off the other end, you can never return to the person you were before. Irina—the one who runs off with Ramsey, the professional snooker player—finds herself sneaking back into the apartment she shared with her longtime partner, Lawrence, just to sit for a while in the life she once led. "Irina wasn't really visiting Lawrence," Shriver writes, "but herself."
These are modern novels about affairs—no drinking arsenic or throwing themselves in front of trains for these women—and, as such, they explore the conundrum of a successful partnership today: how to remain close enough to feel consoled and distant enough to remain intrigued—and intriguing.
But as with Madame Bovary and Anna Karenina, the decisions, even the simple ones, are fraught. In Miller's novel, Meri, thinking about the elder couple next door, finds herself "yearning to have, to have had, even the pain that Delia clearly had, if that's what had made it possible for her also to have something as moving, as thrilling, as rich as the love that existed between her and Tom." Shriver makes this point even more stridently by exploring both options—faithfulness and faithlessness—so thoroughly and finding that there is no escape from life and its humbling compromises.
Perhaps, then, when we yearn for an exit from the confines of commitment, we should remember also the pleasures of stability. That solid rock underneath it all. "'Security' was often cited disapprovingly as the reason that some women stayed in bad marriages, implying security meaning money, an arrangement just shy of prostitution. Too, folks who opted for security supposedly traded adventure and spontaneity for a spiritual subsistence that was pat and dead," Shriver writes. "But for Irina and Lawrence, achieving any semblance of security had been hard work. Safe haven was probably hard-won for most people, whose refuges were far frailer than they appeared.... It stood to reason, then, that security was a more precious commodity than its plodding reputation would suggest—and that it was profligate to treasure safety only in retrospect."
