The original was sort of a science-discovery idyll with a courtroom drama tacked on at the end? I think? This version drills right down into the courtroom vein and sticks there: Scalzi's Jack Holloway is a disbarred lawyer, arguing contractual points with his ZaraCorp manager right from chapter one. He's also a smartass, a showboat, and irritating. Not incidentally, this makes for some bouncy fun courtroom scenes. Really, nothing in this book is incidental. All the ducks -- or, should I say, all the charges are planted in a neat line and fire on schedule. (Triggered by... but that would be telling.)
I suspect, in the end, that Scalzi is having fun with the 50s pulp portrayal of the rugged individualist SF hero. Holloway is that, in an updated context; the text is not shy about what that means and what he is good for. And at. And what he's not. What kind of person he really is, the text leaves in your hands. It's a charming ride, anyhow.