The 99-year-old poet Lawrence Ferlinghetti, one of the last surviving members of the Beat generation, has sold an “experimental” new novel to a major American publisher, and it is due out in time for his 100th birthday.

Ferlinghetti, one of the US’s best-loved poets and a veteran of the second world war, told the New York Times that the book, Little Boy, was “not a memoir, it’s an imaginary me”. He added: “It’s an experimental novel, let’s put it that way … It’s the kind of book that I’ve been writing all my life.”

The paper said the book had a “headlong, often stream-of-consciousness style”, describing it as a mix of autobiography, literary criticism, poetry and philosophy.

The author of more than 30 poetry collections, including the bestselling A Coney Island of the Mind, Ferlinghetti co-founded the City Lights bookshop in San Francisco in 1953 and went on to publish works including Allan Ginsberg’s Howl – for which he was arrested on obscenity charges – through the City Lights publishing house.

The recipient of a lifetime achievement award from the National Book Critics Circle, and the Literarian award for “outstanding service to the American literary community”, Ferlinghetti even has a street named after him in San Francisco. But despite the acclaim in which he is held, Little Boy’s path to publication was not entirely smooth. Ferlinghetti’s agent Sterling Lord – who is 97 himself – initially failed to sell the partial manuscript, despite receiving interest from six publishers.

But Lord, who represented Jack Kerouac in the 50s and initially found that every major publisher rejected his seminal novel On the Road, persevered. “I felt it was a crime to let it sit there,” Lord told the New York Times. “I said, ‘Lawrence, it’s too good, I want to take it out and try again.’ And he said, ‘See, that’s why you’re the best agent in town!’”

Last month, Lord received an offer from Doubleday’s Gerald Howard, who described the book as “like nothing I’d ever read before”.

Howard told the New York Times: “I think of it as a closing statement: ‘This is who I am, this is what I experienced, this is the way it looks to me.’ It’s not just the fact that he’s 99 years old that gives it authority, it’s the life he’s crammed into those 99 years.”

Little Boy will be released next March, when Ferlinghetti will turn 100.