["The Half-Sisters"] is a snazzy, delightful novel, jaunty as a roadster and with something of its period flavor. It starts off in 1937 when its two 11-year-old heroines, energetic girls both, are spending August together as usual. They are related by marriage but not by blood—Erica's father has married Billie's mother—and are complementary rather than identical, Erica being plain, good and sensible, Billie stunning, bad and impulsive….
Listening to Cynthia Propper Seton recount their ups and downs, their betrayals, dishonesties, loyalties and illuminations, is like listening to a witty, well-traveled, sophisticated and slightly eccentric rich aunt gossiping and passing judgments upon her acquaintances, a fascinating passtime when the aunt has the flair, style and pithiness of the author. Also you learn things. She reminds me a little of Mary Poppins—no nonsense, please—and also of Lord Chesterfield, as she delivers verbal fillips to her characters' egos with 18th century elegance and precision, then injects them with helpful epigrams. The setting, too, has its elegances: it's the kind of world in which people have large flats in New York and spend the summer yachting at Moriches, and the author, polite or innocently snobbish, assumes we all know all about it. This plebian didn't, but it's great fun to watch, especially since the point, as in tennis (Billie's game), is not the activity or the content but the polish. Seton does not waste our time.
The overview that emerges is a comic one, although muted by a sense of the great futilities lying beyond its perimeters. Life is a series of choices you didn't intend to make, can't see beyond and end up being trapped by, and one of the most important things you can learn (especially if female) is how to accommodate, how to compromise with grace. The "role models" (Erica would find this phrase intolerably sloppy) tend toward strong-willed women whose lives nevertheless don't quite work out, and men who are weak of chin or insensitive as stuffed rhinoceroses, though there are a few admirable exceptions. Womens Lib is not something these women go in for, but the daughters do. They thereby become, apparently, pains in the neck (Seton is hard on political simplistics of any kind). But good Erica does have her liberating moment: having spent all her life "taking orders," doing what she thinks she ought to do, she finally does something she wants to do. It happens to be sleeping with her husband's brother, and since "The Half-Sisters" is a comedy of a kind, she is not punished for it.
The jacket cover indicates that this is Seton's second novel. Having been so amused and informed by it—I was sorry when this quirky aunt got up to go, still keeping some of her secrets to herself—I wish I had read the first one.
Margaret Atwood, in a review of "The Half-Sisters," in The New York Times Book Review (© 1974 by The New York Times Company; reprinted by permission), May 5, 1974, p. 7.