IN THE DECADE following Emily Dickinson’s death, most of her correspondence went up in flames. Lavinia Dickinson, the poet’s sister and companion, followed Emily’s directives and burned the entire cache of letters that the poet had received. Few copies of Dickinson’s own epistles survived, and many that did were the victims of “scissored deletions” — words and phrases were delicately but deliberately sliced from the text. It’s clear that Lavinia and Austin Dickinson, Emily's brother, were the most likely culprits, and that they sought either to censor or protect (or perhaps, both) their eccentric sister. What’s not clear, however, is exactly what was excised from those hole-ridden letters, and what biographical information existed in those papers that were destroyed entirely.

It is no surprise then, that the scholarly study of Dickinson’s correspondence has long been fraught with misunderstandings, errors, and faulty guesswork. A sly writer, Dickinson rarely dated her poetry, conceived multiple “rough” and “fair” copies of her letters, and often wrote in a sort of code about which her biographers can only speculate. While much of the groundwork has been laid — nearly all of the surviving correspondence has been sorted and dated, for instance — various riddles remain unsolved.

Of course, Dickinson’s extraordinary life often confounds — and motivates — biographers who seek to find patterns among the correspondence and then apply those patterns to fill in the (often literal) biographical gaps. Her reclusive lifestyle, habit of dressing only in white, and “nervous” nature have created a mythology all their own — a puzzle which scholars often seek to dismember and decipher, using her enigmatic verse as an instruction manual. “Figuring out” Emily Dickinson has become an industry of some size and consequence.

Even in her own lifetime, Dickinson’s nontraditional lifestyle as a single woman who saw few visitors and grew increasingly homebound as she aged aroused gossip and speculation among her Amherst neighbors, who dubbed her “the Myth.” Ever since her death, scholars and biographers have struggled to determine what exactly filled Dickinson’s time (often without being able to avoid condescension; John Crowe Ransom called her a “little home-keeping person”). The poet’s niece, Martha Dickinson Bianchi, more than any other biographer, disseminated (and perhaps created) the legendary tales that now accompany any biography of the poet. In works such as the Letters of Emily Dickinson and Emily Dickinson Face to Face, Bianchi perpetuated stories of Dickinson’s isolation from the world (“I do not cross my Father’s ground to any House or town”), hinting along the way that dashed romantic hopes had forever dampened Dickinson’s spirit. From here it was but a short leap for many essayists to conclude that the poet had been romantically scorned, and that her poetry was merely a byproduct of a love-stricken maiden. Dickinson’s romantic life — or lack thereof — and her writing became inextricably linked.

One particular set of letters has always aroused special curiosity among Dickinson scholars and readers who wish to understand the poet’s character. The “Master Letters” are a set of three emotionally laden notes addressed to a figure whom Dickinso...