Fans of Zelda, Nancy Milford's groundbreaking (and bestselling) biography of F. Scott Fitzgerald's tortured wife and muse, have been waiting impatiently since 1970 for Milford's promised follow-up about poet Edna St. Vincent Millay (1892-1950). It's finally here, and they will not be disappointed. Milford's vivid narrative limns an electric personality with psychological acuity while capturing the freewheeling atmosphere of America in the turbulent years following World War I. After "Renascence"...