Definitely not as good as the original three. Not enough Salander, and I disagree with the author's choice to 'ship' her and Blomkvist again. I should've checked before reading, but the author's Acknowledgments at the end thanked Larsson's brother and father. It was Larsson's girlfriend who had all of his notes and the manuscript of the fourth novel.
I would not recommend unless you're a completist and HAVE to read it.