J.D Salinger, the shadowy author best known for his magnum opus The Catcher in the Rye, will posthumously release at least five new books before 2020, according to claims in a new film and book set for release next week.

Mr Salinger, who died in 2010 aged 91, was known for his intensely private lifestyle,  though fans were adamant that the writer had a wealth of unpublished works. A new documentary and book, both titled Salinger, claims that Salinger instructed his estate to publish at least five additional books in a sequence intended to begin from 2015.

One collection to be called The Family Glass would add five new stories to the writer's oeuvre, while another is intriguingly title The Last and Best of the Peter Pans. Salinger is also thought to have penned a novel set during World War II, and a novella modelled on his own war experiences.

Thus far, Matthew Salinger - Mr Salinger's son - has declined to discuss plans for new books, while his widow Colleen O'Neill has also declined to comment. In an interview earlier this year, Matthew said he was sceptical that the book and documentary would deepen the public's understanding of his father, who is said to have confined his intimate dealings and private conversations to a circle of just seven or eight people.

However, documentary filmmaker Shane Salerno - who spent nine years researching and filming the movie - is certain that his collection of Salinger's unpublished photographs, hundreds of letters and a handwritten diary - represents the highest quality research. "If that's not the inner circle, I don't know what is the inner circle," he told the Los Angeles Times last week.