Sobol died in Miami from natural causes July 11, with his wife Rose by his side, his son John Sobol told The Associated Press Monday.
Sobol's series featured amateur sleuth Leroy "Encyclopedia" Brown, who would unravel local mysteries with the help of his encyclopedic knowledge of facts great and small. The books, first published in the early 1960s, became staples in classrooms and libraries nationwide. They were translated into 12 languages and sold millions of copies worldwide.
"Thanks to Donald, generations of children have learned to read and solve mysteries alongside Encyclopedia Brown, one of the most iconic characters in children's literature," said Don Weisberg, president of Penguin Young Readers Group, which publishes Sobol's books.
The Encyclopedia Brown books also featured Brown's friend and detective partner, the tough and athletic Sally Kimball. John Sobol said his father was ahead of his times in creating a strong female character.
"That was groundbreaking back in 1963 when the series was first published," Sobol said.
Next year marks the 50th anniversary of the Encyclopedia Brown series. Donald Sobol's latest Encyclopedia Brown adventure, "Encyclopedia Brown and the Case of the Soccer Scheme," will be published in October, according to a release from Penguin.
Sobol was a New York City native. He served in the Army Corps of Engineers during WWII and graduated from Oberlin College. He later worked as a copywriter at the New York Sun, where he eventually worked his way up to reporter. His first Encyclopedia Brown book was rejected two dozen times before it was published, his son said.
In 1958, Sobol became a successful syndicated columnist with his "Two Minute Mystery" series before publishing "Encyclopedia Brown Boy Detective" five years later to launch the most popular series of his career. He and his wife moved to Miami in 1961.
The Encyclopedia Brown concept - in which the solutions to the mysteries are shown after the story - came to Sobol while he was researching an article at the New York Public Library, and a clerk mistakenly handed him a game book, with puzzles on one side and the solutions on the other.
Sobol decided to write a mystery series with the same premise. He earned an Edgar Award from the Mystery Writers of America award for the Encyclopedia Brown series.
John Sobol said his father would frequently test out story ideas on his four children. "We would talk about it sitting around dinner," he said, adding, "My mom also helped inject humor into the stories."
The series inevitably attracted Hollywood, which tried for decades to adapt the books for the big screen, with Anthony Hopkins, Chevy Chase and Goldie Hawn among those interested in the project. But legal disputes over who controls film rights have prevented any feature film from being made.
Sobol's work never brought him the financial success of blockbusters like the "Harry Potter," series, his son said, but his father loved hearing from countless librarians and parents about children who hated to read until they picked up an Encyclopedia Brown book.
Sobol authored more than 80 books and wrote on a daily basis to the very end.
His family has asked that donations in his memory be made to The New York Public Library at www.nypl.org/donaldsobol. Check donations can be mailed to The New York Public Library, 476 Fifth Avenue, Room M-6, New York, NY 10018, payable to The New York Public Library.
Hillel Italie contributed to this report from New York.