No Regrets: The Life of Marietta Tree.

• Author: McElwaine, Sandra

By Caroline Seebohm Simon & Schuster, $27.50

Marietta Tree was the quintessential WNSP--a glamorous, freewheeling spirit born into the stern, judgmental Peabody clan, one of Boston's finest families. Nee Mary Endicott, Marietta was the rebellious only daughter of a reserved Episcopal minister, a parsimonious and austere mother, and most importantly, the granddaughter of the revered Rector of Groton. An effervescent, leggy blonde, Marietta was an accomplished flirt and irresistible to men from an early age. At Groton she created havoc when she appeared in the dining room or at the playing fields, and in her later years she remained the center of attention, pursued and surrounded by admirers and beaux.

No Regrets, which chronicles Marietta's life, is packed with famous names, places, parties, and political intrigue and reads like a Who's Who of the 20th century. It should have been the stuff of fairy tales, but unfortunately it is not. With access to family and close friends, letters, diaries, and engagement books, author Caroline Seebohm pierces the mystique surrounding Marietta to reveal a troubled woman who led a hidden life: clandestine love affairs, estrangement from her four brothers and two daughters, guilt and anxiety over a loveless childhood, emotional isolation, and two failed marriages. To avoid reality, Marietta filled her time with frenzied activity, social and political, and when she at last succumbed to cancer in 1991, at the age of 74, she was filled with remorse as she tried to retrieve her relationships and re-spool the threads of her past. Seebohm's book, therefore, although extremely well written, is wrongly titled. With Regret would be much closer to the truth.

Unlike many of her rich, spoiled friends, Marietta grew up in a strict and frugal household. Her mother was appalled when a guest once asked for two lumps of sugar. Although the Peabodys were socially supreme, they were not well-off and frequently depended on wealthy relatives. As a result, saving face and keeping up a good front formed the core of Marietta's personality and she retreated behind a mask of impervious charm. Unable to accompany friends on expensive trips and forced to wear the same evening gown to opulent debutante balls put a crimp in Marietta's adolescence, but she rarely complained and set her sights on financial freedom and a career in the Foreign Service. She was later crushed to discover she could enter only by marrying into it.

At 19...