The Decatur, Ga., woman died Thursday in Emory University Hospital in Atlanta, said her son, David Dukes of Decatur.
"She was the greatest mother in the world," Mr. Dukes said. "She did everything in the world for me. She was just a really delightful person, everybody was charmed by her."
Mr. Dukes said his mother had a "real appreciation for Southern justice," which led her to write about events in Georgia and Alabama history.
Ms. Barnes wrote the 1976 book Murder in Coweta County, which detailed the first time in Georgia history that testimony from two black field hands helped convict a prominent land baron for the murder of a sharecropper.
The book, which won an Edgar Allen Poe award, was made into a 1983 television movie starring Johnny Cash and Andy Griffith.
In 1987, she penned her autobiography, A Buzzard is My Best Friend, detailing her life as a farmer, Mr. Dukes said.
In 1992, she wrote The Tragedy and The Triumph of Phenix City, Alabama, which examined the city's political turmoil of the 1950s. The book includes the 1954 Phenix City assassination of the Alabama Attorney General-elect Albert Patterson.
"Her book ... has added a tremendous amount to the history of Alabama, and what she's done here is good and will be a lasting thing in the history of the state of Alabama," said Mr. Patterson's son, former Alabama Gov. John Patterson. "Her book also is a lesson for any community who lets its community get in the shape that Phenix City was in. She exposes what was really bad in a place that's been taken over by organized crime."
Services are today in Newnan, Ga.
Survivors include two sons, Mr. Dukes of Decatur and Steven Dukes of San Francisco; brother William "Billy" Barnes of Marietta; sister Clare Medlin of Orlando, Fla.; and one granddaughter.