I love this book! I'm not even halfway thru it, and I'm ready to buy the rest of the series. It's not "hard" sci fi, but it does have a lot of well researched mathematics in it, enough to keep a hard sci fi fan happy. To a previous reviewer who commented about global warming being real and the U.S. being the bad guy, I didn't get that at all from the book. Yes, it was mentioned that global warming turned out to be real, and that the U.S. had to spend lots of money to get it under control, but I don't think the author was preaching on either subject. It was simply a (very small) part of the storyline. In fact, so far, it has been mentioned only once. I recommend this book to any sci fi fan!