A rare edition of "Swann's Way" by Marcel Proust along with letters revealing the unabashed self-promotion of the French literary master fetched 535,500 euros ($623,000) at auction on Monday, Sotheby's said.

The book, which had been valued at between 400,000 and 600,000 euros, is one of only five numbered copies, the first tome of Proust's voluminous "Remembrance of Things Past".

It was printed on washi, the prized handmade Japanese paper, and published in 1913.

Three copies of the edition are privately owned, while another disappeared during World War II.

Bound into the back of the copy auctioned by Sotheby's were eight documents handwritten by Proust, showing his little known mercenary side.

They are mainly letters to friends in the Parisian press asking them to publish glowing reviews -- penned by Proust himself, who even offered money for the articles, while imploring the editors to keep mum.

Proust described "Swann's Way" as "a little masterpiece" and spoke of himself in the third person: "What Mr Proust sees, senses, is entirely original..."

The praise, unsigned, appeared on the front page of the Journal des Debats, and cost the author 660 francs at the time -- or around 2,000 euros ($2,300) today.

He paid another 300 francs for a brief review that appeared on the front page of Le Figaro.

In a letter to his publisher Louis Brun, Proust complained bitterly that the newspaper deleted the adjective "eminent" he had used to describe himself.

Jean-Yves Tadie, a Proust expert who oversaw a 1988 re-edition of "Remembrance of Things Past", said the author "understood before everyone else the importance of... publicity and media relations".

"He spared no expense and did not shy away from what looks to us today like active corruption," Tadie wrote for the Sotheby's catalogue.

Sotheby's manuscript expert Benoit Puttemans told AFP that paying for favourable reviews was commonplace at the time.

Proust had struggled to find a publisher, suffering multiple rejections before Maison Grasset took him on in November 1913 -- if he footed the bill.

Surprised by the success of the book, the Gallimard publishing house lured Proust away from Grasset, which led to the author winning the Goncourt Prize, France's prestigious literary award, in 1919.

Source: AFP