Although promoted by its publisher and initially described in media reports as a sequel to Lee's best-selling novel, To Kill a Mockingbird, which was published in 1960, Go Set a Watchman is actually that novel's first draft. The novel was finished in 1957 and purchased by the J.B. Lippincott Company. Lee's editor, Tay Hohoff, although impressed with elements of the story, saying that "the spark of the true writer flashed in every line", thought it was by no means ready for publication. It was, as she described it, "more a series of anecdotes than a fully conceived novel". In his Times article on Hohoff, Jonathan Mahler recounts that Hohoff thought the strongest aspect of Lee's novel was the flashback sequences featuring a young Scout, and thus requested that Lee use those flashbacks as a basis for a new novel. Lee agreed, and "during the next couple of years, Hohoff led Lee from one draft to the next until the book finally achieved its finished form and was retitled To Kill a Mockingbird."
According to Mahler, "Ms. Hohoff also references a more detailed characterization of the development process, found in the Lippincott corporate history: 'After a couple of false starts, the story-line, interplay of characters, and fall of emphasis grew clearer, and with each revision—there were many minor changes as the story grew in strength and in her own vision of it—the true stature of the novel became evident.' (In 1978, Lippincott was acquired by Harper & Row, which became HarperCollins, publisher of Watchman.)" Mahler remarks that "there appeared to be a natural give and take between author and editor. 'When she disagreed with a suggestion, we talked it out, sometimes for hours,' Ms. Hohoff wrote. 'And sometimes she came around to my way of thinking, sometimes I to hers, sometimes the discussion would open up an entirely new line of controversy.'"
In terms of the initial characterization of Atticus as a segregationist, an element to his character that was dropped in the later draft, there are various theories already offered. Mahler offers that it could have been Hohoff that inspired the change. Raised "in a multigenerational Quaker home near Prospect Park in Brooklyn, Hohoff attended a Quaker school, Brooklyn Friends. Such an upbringing suggests certain progressive values. But probably the clearest window into her state of mind when she was coaching Ms. Lee through the rewrite of Mockingbird is the book she was writing herself at the time: a biography of John Lovejoy Elliott, a social activist and humanist in early-20th-century New York who had committed his life to helping the city's underclass. The book, A Ministry to Man, was published in 1959, one year before Mockingbird."
Michiko Kakutani made note of the changes between the two versions: "Some plot points that have become touchstones in Mockingbird are evident in the earlier Watchman. Scout's older brother, Jem, vividly alive as a boy in Mockingbird, is dead in Watchman; the trial of a black man accused of raping a young white woman ... is only a passing aside in Watchman. (The trial results in a guilty verdict for the accused man, Tom Robinson, in Mockingbird, but leads to an acquittal in Watchman.)" She continues, "Students of writing will find Watchman fascinating for these reasons: How did a lumpy tale about a young woman's grief over her discovery of her father's bigoted views evolve into a classic coming-of-age story about two children and their devoted widower father? How did a distressing narrative filled with characters spouting hate speech (from the casually patronizing to the disgustingly grotesque—and presumably meant to capture the extreme prejudice that could exist in small towns in the Deep South in the 1950s) mutate into a redemptive novel associated with the civil rights movement, hailed, in the words of the former civil rights activist and congressman Andrew Young, for giving us 'a sense of emerging humanism and decency'?"
Kakutani also goes on to describe that not only are characterizations and plot points different, the motivation behind the novel shifts as well, stating: "Somewhere along the way, the overarching impulse behind the writing also seems to have changed. Watchman reads as if it were fueled by the alienation a native daughter — who, like Lee, moved away from small-town Alabama to New York City — might feel upon returning home. It seems to want to document the worst in Maycomb in terms of racial and class prejudice, the people's enmity and hypocrisy and small-mindedness. At times, it also alarmingly suggests that the civil rights movement roiled things up, making people who "used to trust each other" now "watch each other like hawks".
According to Kakutani, "Mockingbird, in contrast, represents a determined effort to see both the bad and the good in small-town life, the hatred and the humanity; it presents an idealized father-daughter relationship (which a relative in Watchman suggests has kept Jean Louise from fully becoming her own person) and views the past not as something lost but as a treasured memory. In a 1963 interview, Lee, whose own hometown is Monroeville, Ala., said of Mockingbird: 'The book is not an indictment so much as a plea for something, a reminder to people at home.'"
The papers of Harper Lee's literary agents in the 1950s, Annie Laurie Williams and Maurice Crain, are held by Columbia University's Rare Book & Manuscript Library. Their records show that Go Set a Watchman was an early draft of To Kill a Mockingbird, and underwent significant changes in story and characters during the revision process. Harper Lee was writing Go Set a Watchman in January 1957, and sold the manuscript to the publisher J. B. Lippincott in October 1957. She then continued to work on the manuscript for the next two years, submitting revised manuscripts to her literary agents. At some point in that two-year period, Lee renamed her book To Kill a Mockingbird. Some of these records have been copied and posted online.