When “The Sopranos” went dark for the last time on HBO, many fans wondered how the premium cable channel would replace the bloodthirsty families dueling to the death over money, power and honor. Ponder no more. This weekend, the premium channel offers its new. multi-part “Game of Thrones,” based on the best-selling series by George R. R. Martin, with gore, lust and epic violence on a scale rarely seen on the small screen.

What’s new? More than a soupçon of science fiction and fantasy. The question is, will audiences tune in for such a shift in tone and venue? The novels, collectively known as “A Song of Ice and Fire,” recount sprawling, multi-generational battles over illustrious thrones and kingdoms, set in mythic times with lurking mystical elements. But lest anyone think this is merely a videogame brought to life – dragons and dungeons with pretty princesses and evil lords dueling dark magical forces – the story is aimed squarely at a mature, adult audience, executive producer David Benioff told reporters during January’s Television Critic’s Association in Pasadena.

“George’s fantasy is not a for-children fantasy. It’s sexy and it’s violent and it’s brutal, and none of the characters are safe,” he says. “Characters that you might think are going to go on for six seasons meet an early end. You think of all those shows that have done that kind of putting-character-in-jeopardy drama, who has done it best? It’s been HBO, in ‘The Sopranos.’ One of the things that was so exciting about tuning into ‘The Sopranos’ or ‘The Wire’ is you never knew who was going to get whacked. [Game of Thrones is] not a gangster show, but it’s got elements of that within it.”

Mr. Martin, series author and and show consultant, suggests the time is ripe for fantasy on the small screen. “Television is full of lawyer shows and medical shows and situation comedies, but fantasy shows … fantasy is something that’s been largely restricted to books for a long time,” he says.

Producers say Martin’s fan base already extends beyond the traditional fantasy lover. Mr. Benioff describes an email he received from a man he met at a wedding, where he had mentioned he was working on the series. “He sent me this two-page e-mail about how excited he was. It’s the dean of Stanford Law School, who is completely obsessed with George’s books,” he says. “There’s something about them. Even people who aren’t normally into fantasy – like my 72-year old father who, because I was working on the series, started reading the books – is now a complete addict,” he adds.

This particular swords-and-horses fantasy speaks to women as well, says 24 year-old marketing professional Anna Daugherty via email. She says her fiancé introduced her to the series. “After I hit the first 100 pages or so, I was hooked,” she says. “Nobody is truly a villain, just as no one is truly good. Everyone has their own agenda. Even the children are well-written,” she says. She and a friend plan to pitch in together to subscribe to HBO “so we can have watching parties.”

Fantasy for adults is well on its way into the mainstream, says Boston public relations expert Michael Fearon, who points out that “Lord of the Rings” proved the genre could draw a mass audience. Beyond that, he says, “historical series have really gained momentum on the cable networks,” pointing to 'Spartacus,' 'Rome,' and 'The Borgias.' “Although Game of Thrones is not history," he says, “its mythological ties bring viewers back to our ancestors’ epic tales, like The Odyssey, Gilgamesh and Beowulf.”

Keith Kornell, author of “Super Born: Seduction of Being,” a fantasy novel for adults, says this is a good time for fantasy and superheroes. He points to the two broadcast TV shows, “The Cape” and “No Ordinary Family,” about humans with superpowers. “As we deal with our mounting frustrations – due to economic problems, idiot politicians, screaming TV pundits, a failing education system and more – we need relief and hope,” he says. “Superheroes and escaping into fantasy help us believe that there is hope, even when we know it’s a fantasy.”