Russell Hoban, an inventive American author who penned tender picture books about a badger named Frances before writing “Riddley Walker,” an acclaimed novel about a post-apocalyptic world, died Dec. 13 in his adopted home town of London. He was 86.

He was admitted to a hospital for congestive heart failure, but the exact cause of death has not been determined, his daughter Phoebe Hoban said Thursday.

In his five decades as a writer, Mr. Hoban drew comparisons to fantasy authors J.R.R. Tolkien and C.S. Lewis. He shared their basic philosophy that children’s literature, and imagination, need not be only for the young.

“At his best,” Washington Post book critic Michael Dirda wrote in 1997, Mr. Hoban “is the finest all-round writer in the world.”

Once an illustrator for magazines including Time and Newsweek, Mr. Hoban established himself as a children’s author in 1960 with “Bedtime for Frances.” In other books in the series, he let the adorable badger guide her young readers through universal rites of childhood.

His book “The Mouse and His Child” (1967), about discarded toy mice trying to find a new home, is widely considered a classic of young adult literature.

In the late ’60s, Mr. Hoban moved to London in part, he said, to summon inspiration from the ghosts of Victorian England. There he underwent a transformation and began writing the adult fiction that largely defined the rest of his career.

“Riddley Walker,” a novel set in England after a nuclear holocaust thousands of years in the future, made him a literary sensation in 1980. His most stunning achievement was the invention of a new language — the English dialect spoken by the young narrator.

On the page, the language looked like “Chaucer in need of a spell-check,” writer Peter Carey once noted. Read aloud, the words came to life and revealed the poignant details of everyday life.

“Counting counting they wer all the time,” Mr. Hoban wrote, describing pre-apocalypse mankind. “They had iron then and big fire then had towns of parpety. . . . They had the Nos. of the rainbow and the Power of the air all workit out with counting which is how they get boats in the air and picters on the wind.”

Mr. Hoban was so beloved by his readers that, on his birthday, they sprinkled the London subway and other locations with sheets of yellow paper bearing quotations from his works. Mr. Hoban always wrote his manuscripts on yellow paper, his daughter said.

“Riddley’s” success was difficult to top. Mr. Hoban once told the Guardian newspaper that after “Riddley,” everything was “an anticlimax.”

Mr. Hoban never stopped writing; in all he wrote dozens of children’s books and a shelf full of novels. His other noted books included “Turtle Diary” (1975), whose characters try to release turtles from a zoo, and “Pilgermann” (1983), about a eunuch on a pilgrimage to the Holy Land.

Russell Conwell Hoban was born Feb. 4, 1925, in Lansdale, Pa., to Ukrainian Jewish immigrants.

Mr. Hoban showed early promise as an artist, a future that his parents strongly encouraged. After attending art school in Philadelphia, he joined the Army.

Before shipping out to Europe during World War II, he burned his copies of his favorite childhood books, including “Treasure Island” and “Arabian Nights.”

“That was the end of boyhood,” he told the Guardian. “I loved those books but I sacrificed them on the altar of manhood.”

His decorations included the Bronze Star Medal.

After the war, Mr. Hoban began his career as an illustrator. His portraits of entertainer Jackie Gleason, singer Joan Baez and others appeared on the cover of Time magazine.

Mr. Hoban collaborated on the Frances series with his first wife, the illustrator Lillian Aberman Hoban, from whom he was later divorced.

Survivors include his wife of 36 years, Gundula Ahl Hoban of London; four children from his first marriage, Phoebe Hoban and Julia Hoban, both of New York City, Esme Hoban of Wilton, Conn., and Brom Hoban of Austin; three sons from his second marriage, Jake Hoban of London, Ben Hoban of Exeter, England, and Wieland Hoban of Birstein, Germany; and 13 grandchildren.

Mr. Hoban’s final book, a young adult novel called “Soonchild,” about passing stories from one generation to the next, is forthcoming.

“If I am kept away from writing I become physically unwell,” he told the Guardian in 2002.” It is art and the creation of art that . . . make me feel it is a good thing to be part of the human race.”