Due to its naturalistic, violent subject matter and obsession with the ghosts of the past, Light in August is characterized as a Southern gothic novel, a genre also exemplified by the works of Faulkner's contemporary Carson McCullers, and by later Southern writers like Flannery O'Connor, Truman Capote, and Toni Morrison. However, critics like Diane Roberts and David R. Jarraway view Faulkner's use of Southern gothic genre tropes, such as the dilapidated plantation house and the focus on mystery and horror, as self-conscious modernist commentary on man's "warped relationship with the past" and the impossibility of determining true identity.
According to Daniel Joseph Singal, Faulkner's literary style gradually developed from 19th century Victorian to modernist, with Light in August more firmly grounded in the tradition of the latter. The novel is characteristic of the modernist fascination with polarities—light and dark, good and evil—the burden of history on the present, and the splintering of personal identity. The plot is also divided into dual currents, one focusing on Lena Grove and the other on Joe Christmas, a technique that Faulkner continued to use in other works. The narrative is not structured in any particular order, as it is often interrupted by lengthy flashbacks and constantly shifts from one character to another. This lack of organization and narrative continuity was viewed negatively by some critics. As in his other novels, Faulkner employs elements of oral storytelling, allowing different characters to lend voice to the narrative in their own distinct Southern idiom. Unlike some of the other Yoknapatawpha County novels, notably The Sound and the Fury, Light in August does not rely solely on stream-of-consciousness narration, but also incorporates dialogue and an omniscient third-person narrator that develop the story.
Some critics have speculated that the meaning of the title derives from a colloquial use of the word "light" to mean giving birth—typically used to describe when a cow will give birth and be "light" again—and connect this to Lena's pregnancy. Speaking of his choice of title, Faulkner denied this interpretation and stated,
. . .in August in Mississippi there’s a few days somewhere about the middle of the month when suddenly there’s a foretaste of fall, it’s cool, there’s a lambence, a soft, a luminous quality to the light, as though it came not from just today but from back in the old classic times. It might have fauns and satyrs and the gods and—from Greece, from Olympus in it somewhere. It lasts just for a day or two, then it’s gone. . .the title reminded me of that time, of a luminosity older than our Christian civilization."
Within the novel itself, the title is alluded to when Gail Hightower sits at his study window waiting for his recurring vision of his grandfather's last raid. The vision always occurs in "that instant when all light has failed out of the sky and it would be night save for that faint light which daygranaried leaf and grass blade reluctant suspire, making still a little light on earth though night itself has come." The story that would eventually become the novel, started by Faulkner in 1931, was originally titled "Dark House" and began with Hightower sitting at a dark window in his home. However, after a casual remark by his wife Estelle on the quality of the light in August, Faulkner changed the title.