The Millennium series by David Lagercrantz is a continuation of Stieg Larsson's original Girl with the Dragon Tattoo trilogy. In these thrilling novels, Lagercrantz takes readers back into the world of Lisbeth Salander and Mikael Blomkvist, as they face new challenges and uncover more dark secrets. With complex characters and intricate plots, this series is a must-read for fans of the original trilogy.