The worldwide hit crime trilogy "Millennium" by the late Swedish author Stieg Larsson will have a fourth instalment, Sweden's Norstedts Publishing Group said Tuesday. "We have now decided to let somebody take over and tell what happened next," Norstedts publisher Eva Gedin said in a statement. Swedish author David Lagercrantz, co-author of Swedish football star Zlatan Ibrahimovic's biography "I am Zlatan Ibrahimovic", will be responsible for the new addition, which will hit the shelves in mid-2015, a decade after the first Millennium book was published. "I've already started writing and it's terribly fun," Lagercrantz said in the statemtent. "It's a fantastic world to step into." According to the publishers, the author will continue the same main characters -- Mikael Blomkvist, an investigative reporter, and Lisbeth Salander, a feisty rebel hacker-turned-detective -- as well as some plot lines from previous books, but will also add personal touches. Larsson's longtime partner, Eva Gabrielsson, who has been locked in a bitter dispute with the author's family over his lucrative inheritance, told Swedish tabloid Aftonbladet that she was taken aback by the announcement questioned whether the publisher has the right to commission a follow-up. "I think it's distasteful to try to make more money," she told the paper. According to Gabrielsson, the publishers did not have access to the unfinished fourth instalment that Larsson had started working on before he died in 2004. "So I guess they have started from scratch," she added. The Millennium series became a worldwide phenomenon and was adapted to the screen, first in Sweden and then in the US by filmmaker David Fincher. The first three books have sold 75 million copies in more than 30 languages, according to Norstedts.