Stieg Larsson’s Millennium Trilogy starring the brilliant and enigmatic computer hacker Lisbeth Salander has the taken world by storm. Now, his father Erland, and brother Joakim are scheduled to appear on CBS Sunday Morning this Sunday to share details of a fourth book in the series. After Larsson’s death in 2004, it was revealed that a manuscript for a fourth installment existed, and rumors began to fly about how much of it he was able to develop before being felled by a heart attack. According to an article on the Los Angeles Times website, Erland claims to have seen and held the manuscript. His brother also speaks of receiving an e-mail mere days before the author’s death in which he writes of nearing completion of the book.

The manuscript has been rumored to be located on Larsson’s laptop, and believed to be in the custody of Eva Gabrielsson, his lover of 32 years. The writer died without a will, and his father and brother have been left to battle over his considerable estate with Gabrielsson. The two factions communicate almost exclusively through lawyers, so it is unclear how Erland gained access to the book. Sunday’s interview may shed light on the facts. Or maybe not. Brother Joakim is quoted as saying this fourth manuscript is actually the fifth book of the planned 10-part series, “because he [Larsson] thought that [it] was more fun to write than book number four.” Hmm.

The idea of a fourth Millennium book is as intriguing to Knopf, Larsson’s publisher, as it is to his avid fans. “I’m as curious as the rest of the world,” says executive director of public relations Paul Bogaards. “It’s a subject of much speculation among Larsson readers. At some point, one hopes that there is a finality to the question about the fourth book.”

The Millennium Trilogy continues to dominate the bestsellers lists and garnered three of the top four spots on USA TODAY‘s Best-Selling Books list for the third quarter of 2010.