PARIS - When Eric Jouannest left his book on a bridge behind Notre Dame cathedral, he didn't expect it would wind up in a remote Russian republic.
But such is the globalized nature of a club that started in the United States a few years ago and has spread across the Atlantic and far beyond.
The founders of BookCrossing.com compare their online book club to a virus, one that has reached far-flung places carried by members who heed the philosophy: If you love a book, set it free.
One selling point is that it costs nothing to join. Members include literature buffs determined to share their passion or thin out their shelves and travelers who simply love a good book - although here the books do most of the traveling.
The concept is based on what the club calls its 3R's: Read, Register and Release.
Participants label a book's inside cover with a tracking number and the Web site's address (www.bookcrossing.com) then stash it somewhere and post instructions online explaining where. Once a book's pickup is logged online, an e-mail is automatically sent to whoever dropped it off.
Part of the thrill is seeing how far afield a book can land, said Jouannest, 45, a Parisian sound technician who left a French mystery novel on the Pont de l'Archeveche, a stone bridge behind Notre Dame, one spring day in 2004.
"I got word of it two months later. Someone found it in Ulan Bator - in Mongolia! - and he took it with him to Buryatia," said Jouannest.
Word keeps spreading and membership rising as people leave books in cafes, parks or anyplace else so strangers can find them and partake in a novel attempt to turn the world into one big library - with no late fees.
Sometimes the system works, sometimes it doesn't.
About 25 percent of books are found, according to Ron Hornbaker, an American software developer who founded the site in 2001.
The club now boasts 400,000 members in 120 countries.
"I knew it was the type of thing that could catch on and grow sort of in a viral nature," Hornbaker, 39, said by telephone from his office in Kansas City, Mo. "But I had no idea it would grow as fast as it did and as broadly geographically as it has."
Overseas members now account for the majority. The number of American BookCrossers has dipped to 46 percent, with those in Britain, Canada, Germany, Spain, Italy, France and elsewhere accounting for most of the rest.
Angelo Rinaldi, literary editor of Le Figaro newspaper, said that when he takes a train he often leaves a book behind.
"But I've been doing that for ages," he said. "I didn't know I was a pioneer."