The nine texts by the author of Swann's Way were originally to be part of his first book, Les Plaisirs et les Jours (Pleasures and Days), a collection of poems and short stories published in 1896.
But Proust, who was still in his 20s, later decided not to include them.
The home of the writer's aunt and uncle in Illiers-Combray is now open to the public. Photo: AFP
They were uncovered by Bernard de Fallois, a noted Proust specialist who died last year, and founder of the Fallois publishing house.
It will issue the collection on October 9 under the title The Mysterious Correspondent and Other Unpublished Novellas.
“With this diverse collection of previously unpublished novellas and texts, we discover the sources of Swann's Way,” the house said in a statement.
Bernard de Fallois had previously discovered a Proust novel that went unpublished in his lifetime, Jean Santeuil, as well as an unfinished text called Contre Sainte-Beuve. Both were eventually published in the 1950s.
Proust, who died in 1922 at the age of 51, has been hugely influential for subsequent generations of authors, in particular for the masterpiece In Search of Lost Time, also called Remembrance of Things Past, the first volume of the Swann works.
A copy of that book, dedicated by Proust to his lover, sold at auction in December for €1.51 million, a record for a French book.
The newfound texts show a young writer dabbling in new narrative techniques while exploring such risque themes for the era as physical love and homosexuality.
“Because of their audacity, he probably thought they would offend a social milieu dominated by traditional moral forces,” the publisher said.
The 180-page collection will include facsimiles of the original texts as well as analysis and critiques.