Of our twentieth-century Presidents, William Howard Taft (1909-13) may be the least remembered, and among First Ladies, his wife, Helen Herron Taft, is also a shadowy figure. Yet she has caught the attention of the historian Carl Sferrazza Anthony, and in Nellie Taft: The Unconventional First Lady of the Ragtime Era (William Morrow, 534 pages, $29.95) he presents an appealingly original woman with a lifelong sense of adventure.

In 1900 Nellie took up surfing in Hawaii en route to the Philippines, where her husband had just been appointed governor. When she invited Filipinos to social events, she deflected criticism with a sentiment remarkable for its time and place: “Neither politics nor race should influence our hospitality in any way.” Her strong political instincts helped propel her husband toward the Presidency, and after his victory she broke with tradition by insisting on sitting beside him in the carriage that took them to the inauguration.

Later she shocked her own party by showing a degree of support for the FDR administration. Nellie Taft died in 1943 at the age of 82, her span paralleling, as Anthony shows in his lively biography, a volatile series of changes in American life.