Friends say that he has never stopped writing, although he has not published a word since a collection of short stories in 1965. His second and last novel to appear, in 1961, was Franny and Zooey, featuring the Glass family.
It is thought that at least some of the published novels continue this family's saga.
The claims are made in a BBC2 Close Up arts documentary about the American author, which is to be broadcast tomorrow. Friends and family members also talk for the first time about how fame and his experiences in the Second World War changed him.
Salinger, who is 80 this year, was catapulted to fame after The Catcher in the Rye was published in 1951. It told the story of Holden Caulfield, a disillusioned 16-year-old and his search for something to believe in.
The book has acquired a cult status over the decades, becoming a standard school text at the same time as inspiring fans to travel on pilgrimages to Salinger's home in the county town of Cornish, New Hampshire. It even became the subject of conspiracy theories after a copy was found on Mark Chapman, the man who shot John Lennon. The writer, however, has always fiercely guarded his privacy.
His last interview was given to a 17-year-old schoolgirl, and after it made national news he refused all other media approaches. In that last interview he revealed that The Catcher in the Rye was autobiographical, sparking yet more interest in his life.
When Joyce Maynard was 19 she started corresponding with Salinger and remembers: "It was like Holden Caulfield writing to you."
Ms Maynard later went to live with the writer, and wrote a memoir of their time together, which he saw as a threat to his cloistered existence.
The last words Salinger ever spoke to her were: "The problem with you, Joyce, is that you love the world."Reuse content