The collection of some 120 items from the “Remembrance of Things Past” author's personal archives even includes a hand-corrected proof of one of his well-known works.
The trove of artefacts, being sold by the writer's 41-year-old great-grand-niece Patricia Mante-Proust, is to be auctioned on May 31.
Experts estimate the entire collection will sell for €520,000 to €740,000 ($600,000 to 850,000).
Included are several photos of the author, his family and close male friends Lucien Daudet and Reynaldo Hahn who were also his lovers.
One image shows Daudet casting a dreamy gaze at Proust, while leaning an arm on the writer as another friend stands off to one side.
Proust, on the orders of his parents, was supposed to get back any prints of that photo in circulation because the 1896 picture was deemed compromising.
Also in the collection is one of the most famous portraits of the writer, taken when he was about 17, and which bears an inscription on its back from Daudet that reads: “to my dear Marcel.”
Proust fans will have an opportunity to get their hands on a set of proofs of “In the Shadow of Young Girls in Flower”, the second part of Remembrance, that includes crossed out passages and corrections.
The book, which was supposed to be published in 1914, was delayed by the outbreak of World War I and left the author with time to make changes to the manuscript.
An original edition of “Swann's Way”, the first volume of Remembrance and which was published in 1913, will also go up for sale.
Among the most moving items being put up for auction are two of the three known letters from Proust to his father, who did not see literature as a proper profession.
In a September 1893 missive Proust appears to submit to parental authority by saying he wanted to “seriously” study for foreign service entrance exam.
In another letter, which is from Proust to Hahn, the author says his friend is “truly the person, along with mother, that I love most in the world,” or Daudet.