Gilead is an epistolary novel, as the entire narrative is a single, continuing, albeit episodic, document, written on several occasions in a form combining a journal and a memoir.

Wanting to leave a testament for his seven-year-old son, Ames writes a long letter filled with reflections on his past, faith, and the history of his family.

Likewise, the character of the narrator's grandfather is loosely based on the real-life story of John Todd, a congregationalist minister from Tabor who was a conductor on the Underground Railroad, and who stored weapons, supplies and ammunition used by abolitionist John Brown in his "invasion" of Missouri in 1857 to free a group of enslaved people, and later—without Todd's knowledge or involvement—in his 1859 raid on the U.S. military arsenal at Harpers Ferry, West Virginia.

Symptoms included pronounced chills followed by fever, abdominal tenderness, nausea, general debility, diarrhea, urine retention, and tongue furring.

Regarding Robinson's theological influences in Gilead, she has explained the importance of primary Calvinist texts, particularly Calvin's Institutes of the Christian Religion.

[9] Kirkus Reviews said that "Robinson has composed, with its cascading perfections of symbols, a novel as big as a nation, as quiet as thought, and moving as prayer.

"[10] Publishers Weekly said that "Robinson's prose is beautiful, shimmering and precise; the revelations are subtle but never muted when they come, and the careful telling carries the breath of suspense.

[13] In a poll of US literary critics that was conducted by BBC Culture and had its results shared in January 2015, Gilead was voted the fourth greatest novel written since 2000.

Robinson said in a lecture entitled "The Freedom of a Christian," that she thinks "that one of the things that has happened in American Cultural History is that John Calvin has been very much misrepresented.

"[18] Roger Kimball, in his review of The Death of Adam in The New York Times wrote, "We all know that the Puritans were dour, sex-hating, joy-abominating folk – except that, as Robinson shows, this widely embraced caricature is a calumny".

University of Victoria professor of American Literature Christopher Douglas claims that Gilead builds a "contemporary Christian multicultural identity suitably cleansed of the complexity of [...] 'Christian slavery'.

… And I've told you this—one of my favorite characters in fiction is a pastor in Gilead, Iowa, named John Ames, who is gracious and courtly and a little bit confused about how to reconcile his faith with all the various travails that his family goes through.