THE American beat generation author Jack Kerouac is said to have spent just eight days on active service in the US merchant marines on board the SS Dorchester in 1942; but his short stay furnished him with notes for his first novel and, after nearly 70 years, it has now been published for the first time.

The 158-page The Sea is my Brother, a tale of two young men serving on a voyage from Boston to Greenland, has been known about for some time, but is being described by Penguin, its publisher, as "a unique insight into the young Kerouac and the formation of his genius".

The author himself apparently noted: "It's a crock (of ....) as literature."

Literary critics appeared inclined to agree with the author that the text, although showing signs of Kerouac's future style, is raw and juvenile, as well it might be, given that he was 20 when he wrote it.

The literary critic Stuart Evers said: "It is not a great work of literature. It would never be published today if it wasn't by Kerouac, but it is fascinating as an insight into him as a writer He was just jotting down ideas that he would explore with much more gusto in his later work. There is no real narrative, not much happens, but there are flashes of his later work."

Dawn Ward, the book's editor, said the novel shows a side of Kerouac not normally seen in his books. The manuscript was discovered in Kerouac's archive by his brother-in-law.

Ward said: "It was referred to briefly in letters, but nothing that led anyone to believe that there was this really large volume ... This book is really quite important as it shows how Jack developed his writing process."

The novel joins a growing canon of Kerouac's published works, though it seems unlikely that he ever bothered to lug the manuscript round to publishers, as he did in the 1950s while trying to sell the work for which he is best remembered, On the Road.

Even that book, famously written on a continuous scroll of paper, which brought him celebrity when it was finally published in 1957, was issued in an unexpurgated edition only four years ago and another early work, And The Hippos Were Boiled in Their Tanks, written with William S Burroughs in 1945, only saw the light of day in 2008.

Kerouac described The Sea is My Brother as being about "a man's simple revolt from society as it is, with the inequalities, frustration and self-inflicted agonies", which certainly makes it sound like an archetypal adolescent novel. He noted down such prototype characters as "the vanishing American, the big free by (sic), the American indian, the last of the pioneers, the last of the hoboes".

The book's chief protagonist, Wesley Martin, is, like the author, a college dropout, who he wrote, "loved the sea with a strange, lonely love, the sea is his brother and sentences. He goes down." By contrast, another character, Everhart, "escapes society for the sea but finds the sea a place of terrible loneliness".

The two spend the book arguing, drinking and contemplating isolation, which looks pretty much as though they mirror Kerouac's own life.

After many years mingling with and befriending other writers of the beat generation, such as Burroughs, Allen Ginsberg and Gary Snyder, and much time unsuccessfully trying to interest publishers in his work, he found himself disoriented by the fame On the Road brought him. Observer