If you’ve heard of the fantasy author R.A. Salvatore, you might expect his lair to be a faux-medieval fortress, complete with moat, turrets and an impenetrable iron gate guarded by a stone dragon. Yet the House of Salvatore is no castle. One of fantasy’s most popular authors -- and one of Massachusetts’s bestselling scribes - lives in workaday Leominster, where he keeps the real world close at hand. “I think I’m a pretty well-kept secret,’’ Salvatore says with a mischievous smile. Perhaps you’ve never heard of him (he’s no mainstream phenomenon like J.K. Rowling or George R.R. Martin), but within the niche of fantasy and gaming, R.A. Salvatore is plenty famous. His books have sold some 17 million copies, at the rate of around a million per year. They’ve been translated into a dozen-plus languages, and 24 have become New York Times bestsellers. He’s inked a deal with Wizards of the Coast (the maker of the fantasy role-playing game Dungeons & Dragons) to pen six more Forgotten Realms “Neverwinter’’ books; book 2 came out in October. Meanwhile, his influence on the fantasy marketplace is spreading beyond books. His “dark elf’’ character Drizzt Do’Urden has become iconic, featured in graphic novels and a board game. He’s been tapped by video game companies. There’s even chatter about a movie. And yet, this author of dozens of swords-and-sorcery and science fiction novels resides in a modest, four-bedroom colonial about a quarter mile from his high school. He’d rather hang with his friends and family, and watch the Sox or Pats and coach his softball team than live some posh, sequestered life. “Things don’t really impress me. Memories impress me,’’ Salvatore says with hint of townie in his voice. “It’s not the toys, it’s the people.’’