Wondering about the lives we might have led must be a universal preoccupation, for we know the plot of our lives could have gone in many other directions just as easily. As Robert Frost's famous "The Road Not Taken" reminds us, one key choice can make "all the difference." Anne Tyler launches her latest novel, Back When We Were Grownups, with an intriguing "What if?" using the familiar storybook language suggestive of fantasy, wonder, mystery, and dream: "Once upon a time, there was a woman who discovered she had turned into the wrong person." This story is about how Rebecca Davitch, the woman in question, reaches this conclusion and what she discovers about herself and her life as she explores her own "what ifs."

Rebecca, known as Beck to the Davitch clan, made a pivotal decision in her college days suddenly to leave her mostly platonic and studious boyfriend Will Allenby, whom she seemed destined to marry, for a whirlwind courtship with the older, more settled (divorced with three daughters) Joe Davitch. Tyler places importance not only on this decision, but also on Joe's first strong impression of Rebecca when she makes her first Davitch family appearance at an engagement party. He notices her laughing soon after they arrive and comments, "I see you're having a good time," locking in an incorrect notion of her as easy-going, sociable, fun.

Yet Rebecca had always been studious and thoughtful, like Will, and at heart shy. In marrying Joe, she in fact has to learn to become sociable, for the family business is renting out their large row house ("The Open Arms") and organizing other people's prom, engagement, birthday, and other parties and celebrations. So which is the real Rebecca, she finally begins to wonder, even as a grandmother at age 53, long after Joe dies in a car accident and she has raised on her own her four mostly difficult daughters, who have in turn started their own families.

Because the Davitch clan is large and noisy and in most cases self-centered, she not only must learn to be sociable, but also to cater to everyone's needs except her own. She, in fact, has lost her original sense of herself, trading it for another woman who now seems alien to her, offering rhyming toasts at the endless stream of both family and professional occasions, constantly getting the house repaired (her best confidantes are the plumber and roofer), supervising the parties and often enough saving them from disaster, offering a consoling ear to everyone's problems, and constantly throwing herself into the breach to heal hurt feelings or head off family quarrels.

After Rebecca suddenly wonders how she has become who she is, at a disintegrating family picnic, she finds herself also wondering about the alternate life she never lived. What if she had married Will instead? She begins a recurring dream of riding on a train sitting next to a son she never had, whom she later even names Tristram. "In her dream, she took it for granted that this tall, quiet, gawky young boy belonged to her without question." He shares her features, "and most familiar of all was some quality in his expression, something hopeful and wistful, some sense he felt a little bit outside of things. Didn't she know that feeling!"