PARIS — Giacomo Girolamo Casanova was a gambler, swindler, diplomat, lawyer, soldier, alchemist, violinist, traveler, pleasure seeker and serial seducer.

He was also a prolific writer who documented his adventures and love affairs in a steamy memoir that is considered one of the literary treasures of the 18th century.

Born in Venice, he considered France his adopted country but was forced to flee Paris in 1760 after seducing the wives and daughters of important subjects of King Louis XV and cheating them out of their money.

Now Casanova is back in France, celebrated by the French state.

The original manuscript of his memoirs, “The Story of My Life,” and other writings are on display for the first time at the National Library of France in the exhibition “Casanova — The Passion for Freedom.” He is even being called a feminist.

The story of how more than 3,700 pages of Casanova’s papers ended up in one of France’s most prestigious and proper institutions is one that Casanova himself would have loved.

He wrote the memoirs in the last years of his life. Just before his death at 73 in Bohemia in 1798, Casanova bequeathed his papers to his nephew. In 1821 Friedrich Arnold Brockhaus, one of Germany’s most prominent publishers, acquired them from the nephew’s descendants.

It was assumed in literary circles that the documents had been destroyed in the bombing of Dresden in World War II. But they were carried on a bike and hidden in a bank vault in Leipzig. A U.S. military truck drove them to safety in Wiesbaden.

A complete version was published for the first time in French in 1960, but except for a few scholars with access to the original manuscript, it was forgotten.

Then one day in 2007 the French ambassador in Berlin contacted Bruno Racine, director of the National Library, and told him a mysterious intermediary was prepared to talk about the sale of the memoirs. France was deemed the appropriate destination.

A secret meeting was arranged in a small room in the transit area of the Zurich airport. Thirteen large shallow boxes numbered in gold were laid out on two tables for Racine and his curators.

They contained the hand-written memoirs, as well as a text on a lottery, and a note to the emperor of Austria to end the system of usury and correspondence. The script was often bold and undisciplined. Words were scratched out and underlined; ink blotches stained some pages.

“I was completely ignorant of the existence of this manuscript,” Racine said in an interview. “It had never been put on display. But there was no doubt it was authentic. It was an unforgettable moment. It was almost as if we were in front of a religious relic.”

A French commission unanimously declared the manuscripts a “national treasure” that needed to be purchased. But it took almost 2 1/2 years of roller-coaster negotiations with a number of sources before an anonymous donor provided the finances to buy it.

The deal was hailed by the culture minister, Frederic Mitterrand, as the most spectacular acquisition ever made by a French library. At $9.6 million, it was also the most expensive.

The National Library plans to make all the documents available online, and the Gallimard publishing house will begin publishing a multi-volume series of the memoirs in 2013.

Despite his many adventures, Casanova was best known as a libertine. His first sexual encounter, he wrote, was at 11, when he was groped by the sister of his guardian. During his lifetime he claimed to have seduced 122 women, including a nun.

“As for women, I have always found that the one I was in love with smelled good, and the more copious her sweat the sweeter I found it,” he wrote.

The French are presenting the text as a piece of their cultural heritage and focusing on Casanova as a gifted writer. Mitterrand had his own brush with notoriety after he published a memoir that included explicit descriptions of his sexual activities with young male prostitutes in Morocco and Thailand. (He later said they had not been underage.)

“We are particularly proud of presenting, for the first time ever, this great masterpiece of French literature,” Racine said. “Casanova was a man who loved women, a charmer, not a predator who exploited them. He was always tender, never cruel. A feminist.”

The memoir is considered extraordinary because of its detailed and colorful descriptions of the rich cultural and social life of late-18th-century Europe, including Casanova’s own sexual encounters, duels, visits to royal courts, carriage chases, evasions of arrest and swindles. Along the way he drops the names of his acquaintances, like Jean-Jacques Rousseau.

“Worthy or not,” he wrote, “my life is my subject, and my subject is my life.”

Casanova “always made a point of preserving his independence and never sacrificed it for a woman, a cause or a taste for possession,” the library said in a statement announcing the opening. “The exhibition celebrates sensuality and life, considered as an everlasting feast.”

Racine said that the French authorities did not consider Casanova’s personal morality in their decision to buy the works, adding that they must be placed in their historical context.

“The moral judgment never came up,” he said. “We neither approve nor condemn his behavior. Of course, behavior that was tolerated in the 18th century would be condemned today.”