Go Set a Watchman has polarized critics and fans. An early review by Michiko Kakutani in The New York Times described Atticus' characterization as "shocking", as he "has been affiliating with raving anti-integration, anti-black crazies, and the reader shares [Scout's] horror and confusion". Aside from this reveal, Kakutani does make note that Watchman is the first draft of Mockingbird and discusses how students of writing will find Watchman fascinating for those reasons. A reviewer for The Wall Street Journal described the key theme of the book as disillusionment. Despite Atticus' bigotry in the novel, he wins a case similar to the one he loses in To Kill a Mockingbird.
Entertainment Weekly panned the book as "a first draft of To Kill a Mockingbird" and said "Though Watchman has a few stunning passages, it reads, for the most part, like a sluggishly-paced first draft, replete with incongruities, bad dialogue, and underdeveloped characters". “Ponderous and lurching,” wrote William Giraldi in The New Republic, "haltingly confected, the novel plods along in search of a plot, tranquilizes you with vast fallow patches, with deadening dead zones, with onslaughts of cliché and dialogue made of pamphleteering monologue or else eye-rolling chitchat." In The New Yorker, Adam Gopnik commented that the novel could be seen as "a string of clichés", although he went on to remark that "some of them are clichés only because, in the half century since Lee’s generation introduced them, they’ve become clichés; taken on their own terms, they remain quite touching and beautiful." Maureen Corrigan in NPR Books called the novel "kind of a mess." In The Spectator, Phillip Hensher called Go Set a Watchman "an interesting document and a pretty bad novel," as well as a "piece of confused juvenilia." "Go Set A Watchman is not a horrible book, but it's not a very good one, either," judged the Fort Worth Star-Telegram, citing among other flaws its "overly simplistic" plot.
"It is an inchoate jumble," wrote Alexandra Petri in The Washington Post. "Go Set A Watchman is not, by any stretch of the imagination, a good, or even a finished book. For the first 100 pages it lacks anything that could even charitably described as a plot. . . . [T]he writing is laughably bad. . . . I flung the book down and groaned audibly and I almost did not pick it back up even though I knew I had fewer than 100 pages to go. . . . This should not have been published. It’s 280 pages in desperate need of an editor. . . . If you were anywhere in the vicinity of me when I was reading the thing, you heard a horrible bellowing noise, followed by the sound of a book being angrily tossed down. . . ."
Go Set a Watchman set a record for the highest adult novel one-day sales at Barnes & Noble, which included digital sales and pre-orders made before July 14; B&N did not release the exact number.