Halfway through "Red Comet," Heather Clark's incandescent, richly researched biography of Sylvia Plath (1932-1963), there's a revelatory anecdote that strikes at the heart of the creative partnership between the poet and her husband, British writer Ted Hughes. Newly married, the couple were bewitched by the muse each found in the other; and yet both maintained a critical approach in their close readings.

As Clark observes, "Plath criticized Hughes's poems insightfully and confidently. 'How about another word for 'hideous'? I'd like better something that showed the eyes hideous, as in the fine 'Snake's twisted eye.'  … Hughes responded in kind … he advised her to dispense with unnecessary adjectives. … Her lines should be, above all, 'clear and vivid.' "

Which is to say: They were artists first, spouses second.

Nine years in the making, "Red Comet" takes us on a literary picaresque, drawing on untapped archives, Plath's complete correspondence, interviews with surviving members of the couple's social and professional circles, and, most crucially, on Hughes' journals and letters. From both perspectives Clark evokes how their common purpose rose and later diverged, invaluable reportage missing from other books.

She roams over well-trodden terrain. Raised by a struggling widow in the Boston suburbs, Plath recognized that her intellect and discipline were her most potent weapons to break free of a conventional, modest background. Once again we trek though the poet's stellar academic career; her notorious suicide attempt, brilliantly reimagined in "The Bell Jar" (which Clark views as fundamentally a political novel); Plath's electrifying romance with Hughes while studying literature on a Fulbright at Cambridge. But Clark delves deeper than biographers who have gone before: We see the poet as if peering through the Hubble Telescope for the first time, blurred galaxies and nebulas bursting into crystalline detail.

Yet this gold standard of a biography does something more: "Red Comet" is a page-turner, particularly when Clark shifts to Plath's final two years in England. Despite the demands of two small children, the poet was leaping forward as Hughes embarked on an affair with Assia Wevill, crashing his marriage.

Clark cracks open the myth, probing how Plath's misery, stoked by Hughes' depression, nurtured the work. Plath did not consider her "Ariel" cycle "confessional" but a surrealistic étude. The swift pacing and meticulous storytelling of "Red Comet" limn such landmark poems as "Tulips," "The Moon and the Yew Tree," "Daddy," "Lady Lazarus," the bee sequence, and what was likely her final piece, "Edge." As Clark notes, "The short, unadorned couplets, soothing assonances, and stage-lit, interstellar setting of 'Edge' challenged perceptions about how poetry was supposed to sound, as well as the realities it could reflect and alter."

By centering Plath's evolving command of craft — by focusing on her peerless lyrical ear — Clark peels away clichéd interpretations much as the poet shed her false selves, or as she called them in "Fever 103," "old whore petticoats."

A bravura performance, "Red Comet" is the one we've waited for.

Hamilton Cain is the author of "This Boy's Faith: Notes From a Southern Baptist Upbringing" and a member of the National Book Critics Circle. He lives in Brooklyn.