JD Salinger’s son has confirmed for the first time that the late author of The Catcher in the Rye wrote a significant amount of work that has never been seen, and that he and his father’s widow are “going as fast as we freaking can” to get it ready for publication.

Salinger died in 2010, leaving behind a small but perfectly formed body of published work that has not been added to since 1965’s New Yorker story, Hapworth 16, 1924. Rumours have circulated for years that the creator of one of the 20th century’s most enduring characters, Holden Caulfield, continued to write over the ensuing decades he spent in the New Hampshire village of Cornish, far from public view.

In an exclusive interview with the Guardian, his son Matt Salinger has finally revealed, definitively, that his father never stopped writing and that almost “all of what he wrote will at some point be shared”.

Matt Salinger said his father “teemed with ideas and thoughts … he’d be driving the car and he’d pull over to write something and laugh to himself – sometimes he’d read it to me, sometimes he wouldn’t – and next to every chair he had a notebook.

“He just decided that the best thing for his writing was not to have a lot of interactions with people, literary types in particular,” he said. “He didn’t want to be playing in those poker games, he wanted to, as he would encourage every would-be writer to do, you know, stew in your own juices.”

Matt Salinger, an actor and producer, squashed reports that emerged in 2013 of five new books by his father, including one short story featuring Holden Caulfield and one based on Salinger’s brief marriage to Sylvia, a Nazi collaborator. The reports stemmed from a documentary about the author, to which his closest family did not formally contribute; Matt described the rumours as “total trash” that “have little to no bearing on reality … anyone that understood my father at all would find the idea hysterically funny that he would write a book about his first brief marriage. It’s so far beyond the realm of plausibility.”

He did not reveal specifics about the stories, although it appears likely there will be more about the Glass family, who frequently appear in Salinger’s published short fiction. He described his father’s later work as having “no linear evolution”, saying that “it becomes clear that he was after different game”.

He and Salinger’s widow, Colleen O’Neill, with whom he has joint charge of the literary estate, have been working with the material since 2011. He said it was not ready for publication yet.

“He wanted me to pull it together, and because of the scope of the job, he knew it would take a long time. This was somebody who was writing for 50 years without publishing, so that’s a lot of material. So there’s not a reluctance or a protectiveness: when it’s ready, we’re going to share it,” he said. This will take years, he admitted, though he hopes less than a decade: “I don’t owe an apology, I don’t think, but your readers should know that we’re going as fast as we freaking can … I feel the pressure to get this done, more than he did.”

The unseen writing, Matt Salinger said, “will definitely disappoint people that he wouldn’t care about, but for real readers … I think it will be tremendously well received by those people and they will be affected in the way every reader hopes to be affected when they open a book. Not changed, necessarily, but something rubs off that can lead to change.”

“When my father said that everything he has to say is in his fiction, believe it – it’s there. I think when more of his writing is made accessible, he covers everything that the discerning reader would care about. My job is to help that happen as soon as it can, and stay out of the way,” he said.

He has also worked against the republication of several early stories by his father – stories that Salinger himself had said it would be “unfair” to publish. “Suppose you had a coat you liked and somebody went into your closet and stole it. That’s how I feel,” the author told the New York Times in 1974, following the publication of two volumes of his uncollected works. Matt Salinger described them as “youthful exercises, part of his process, his development as an artist”.

“I don’t do it lightly, it’s no fun,” he said of blocking publication. “I do it because my father would have done it and out of love for him, and out of love and protectiveness for his work and his books.”