Hughes, Ted, New Selected Poems, 1957-1994, Faber and Faber, 1995.

When Hughes came out with this collection, many
readers were surprised to find a selection at the
end of this book of previously unpublished poems
that were unmistakably written to and about his
late wife Sylvia Plath. This comprehensive book
provides an excellent overview of Hughes's entire
career and a first glimpse of the much-sought
"Sylvia" poems.

Plath, Sylvia, The Unabridged Journals of Sylvia Plath, edited by Karen V. Kukil, Anchor Books, 2000.

Kukil, the supervisor of the Plath collection at Smith
College, has carefully transcribed the journals Plath
kept between 1950 and a few months prior to her suicide.
There is perhaps no better way to try to understand
her thoughts, emotions, and feelings about
Hughes than to read them in her own words.

Scigaj, Leonard M., ed., Critical Essays on Ted Hughes, G. K. Hall, 1992.

This book...