Freedman, Diane P., Millay at 100: A Critical Reappraisal, Ad Feminam: Women and Literature series, Southern Illinois University Press, 1995.

This collection of twelve essays addresses major
themes in Millay's work and attempts to evaluate her
stature in American literature. In addition to examining
her poetry, critics include commentary on Millay's
work in other genres.

Milford, Nancy, Savage Beauty: The Life of Edna St. Vincent Millay, Random House, 2001.

Milford's biography is the first comprehensive telling
of Millay's life story. Until this biography, Millay's
sister kept letters and journals out of the public eye,
but she decided to release them to Milford for her authoritative
book.

Thesing, William B., Critical Essays on Edna St. Vincent Millay, Critical Essays on American Literature series, Macmillan Library Reference, 1993.

Thesing's critical volume on Millay's work includes
copies of reviews by her contemporaries and evaluations
by modern critics. In addition to a thorough
introduction...