Elizabeth Barrett Browning. Yawn. That cloying love poem, “How do I love thee?” That portrait where she looks at us sideways, her heavy curls shadowing her face. A Victorian invalid who was the victim of her father’s tyranny. What, really, does she have to do with us today?

Not much, one might think, until one reads poet Fiona Sampson’s brilliant, heart-stopping biography, “Two-Way Mirror: The Life of Elizabeth Barrett Browning,” which reads like a thriller, a memoir and a provocative piece of literary fiction all at the same time.

In the first biography of Barrett Browning since 1988, Sampson places the poet squarely in the midst of the political turbulence that roiled Victorian Britain. Far from being a lovesick, confessional “poetess,” a passive victim or a weak invalid, Sampson’s Barrett Browning was a publicly engaged intellectual, a political activist — even a freedom fighter — immersed in the issues of her era. She was engaged with the consequential movers and shakers of the time and ferocious in the pursuit of her own needs, overcoming the barriers that threatened to block her way — no matter the cost to those she loved. Her fame was not limited to England. She was a celebrity in America. Emily Dickinson read her with admiration, and Harriet Beecher Stowe and Nathaniel Hawthorne traveled to Italy just to meet her. Sampson tells us that if Barrett Browning were not a woman, she would have been appointed poet laureate after William Wordsworth died.

Her public renown stemmed from ambitious work that tackled the themes of race, imperialism, war, economic inequity and gender. Her poem “The Cry of the Children” condemns the abuse of child labor. “Casa Guidi Windows” celebrates the Italian struggle for self-rule. “Aurora Leigh,” her verse novel about a young female writer’s career, exposes the many challenges that face marginalized women, including rape, imprisonment and poverty. “The Runaway Slave at Pilgrim’s Point” depicts the horrors of slavery and helped raise funds for the American abolitionist movement.

For those of us who were taught to revere Robert Browning as a writer of “serious” literature, and to regard his wife, as just that — only his wife — this comes as something of a shock, as does the fact that Robert Browning was the less notable of the two when they eloped to escape her father’s wrath.

Sampson tackles our misunderstanding of Barrett Browning by showing us the challenges she faced. Writing in the present tense, Sampson places “Ba,” as her family and friends called her, before the reader in her full humanity, so that we puzzle over her problems, we are infuriated by the doctors who tell her not to write to preserve her health and we egg her on when it is clear that her father will not let her marry Browning. Sampson also guides us through what she has discovered and points out, with caustic humor, the irony of certain situations. When she describes a critical letter that the 21-year-old Barrett Browning receives from one of her mentors, Hugh Stuart Boyd, Sampson writes:

“The letter itself is lost, but we know something of what it contains from Elizabeth’s reply. Evidently, he’s enclosed some verses in Greek addressed to her, but also expressed interest in her ‘improvement.’ Combining flattery with criticism is, did she but know it, the classic move an older man makes on a younger woman. It works so well because young women are so often in the grip of self-criticism; learning the delicate paradox of excelling at being secondary.”

These authorial asides are always helpful, often provocative and sometimes outright funny. Most importantly, they help Barrett Browning seem more alive, as the two poets’ voices often intertwine on the page.

This would have pleased Ba, as she was fascinated by the idea of talking to the dead, and, in many ways, as Sampson makes clear, this is the impossible quest of the biographer, to engage the dead, to ask them questions and listen for a response. The “real subject” of a portrait, she writes, “isn’t perhaps a person so much as an encounter between two people, the artist and her subject.” And this is exactly how “Two-Way Mirror” reads, as a vividly drawn exchange between a living poet and a dead one. Sampson asks questions that Barrett Browning sometimes answers. Sometimes, of course, she doesn’t, but Sampson’s questions keep the reader turning the page, as we want to know what the answers might be. Throughout this magical and compelling book, Sampson shows us that we, too, can speak to the dead, or, at the very least, we can listen to their words.

Charlotte Gordon’s latest book, “Romantic Outlaws: The Lives of Mary Wollstonecraft and Her Daughter Mary Shelley,” won the National Book Critics Circle Award for Biography.

Two-Way Mirror

The Life of Elizabeth Barrett Browning

By Fiona Sampson

W.W. Norton & Co. 336 pp. $27.95