Fans of Sir Arthur Conan Doyle’s Sherlock Holmes character, who first appeared in 1887’s A Study in Scarlet, were so enthralled by the adventures of the British sleuth and his sidekick, Dr. Watson, that they began writing their own tales involving the pair. Beginning in the late 1960s, Star Trek’s devoted fans, unable to get enough of the Starship Enterprise, began producing their own scripts, running them off on mimeograph machines and selling them at science-fiction conventions. The practice goes beyond no-name devotees, as more well-known writers have likewise borrowed inspiration; Sir Thomas Malory’s Le Morte d’Arthur, which was published in the 15th century, is based on legend, and William Shakespeare was commissioned to write plays based on existing works.

Although the Internet has changed the distribution methods, fan fiction remains anonymous, though most of the participants are young women, says Donna Decker, an English professor at Franklin Pierce University in New Hampshire who studies fan fiction.

Take 22-year-old Michele Tallarita of Whitehall, Pa., for example. She began writing fan fiction in middle school as a way to gain an audience beyond family and friends for the stories she loved to craft.

Her first foray, an original spin on a minor character from the animated movie Spirited Away, flopped. But then she concocted a fight scene between Twilight’s Edward and Jacob and gained instant celebrity. Her short story, or “drabble,” as it’s called in the fan-fic realm, garnered more than 100,000 hits and 1,000 reviews from online readers. She even received a marriage proposal. “It turned into a monster,” she says.

Tallarita credits her online popularity with giving her the confidence to write original fiction. In August, she published her first e-book, Freefly, about a science geek and a girl who can fly. She had hoped her fan-fiction groupies would be willing to shell out $2.99 for a copy, but so far sales have been slow.

“Fan-fiction readers are browsers,” says Tallarita, an MFA student at Temple University. “To get them to reach into their wallets is fairly difficult.”