When Sylvia Plath killed herself early on the morning of Feb. 11, 1963, she left behind two children, an estranged, adulterous husband, a note for the baby sitter and a neat black binder containing 40 poems. The contents of that binder would become Ariel, one of the most devastatingly moving and universally beloved books of poetry published in the 20th century. But the contents of that binder and what we know as Ariel are not quite the same thing.
After Plath died, her manuscript passed to Ted Hughes, who was legally still her husband. Hughes reordered the poems and dropped about...