Book 2 of Old Man's War.
More talking, less action made me like it less than book 1. There were pages I skipped completely because I wasn't interested in the science or rambling exposition. I also skipped some other parts that were about sex, also unnecessary and added nothing to the plot and just made me roll my eyes and wonder if the author had been one of those stereotypical nerds in high school that got rejected by the popular girls and so this was his weird version of revenge or something. I don't know, it's just that the sex scenes and discussions of sex annoyed the hell out of me.
Plot-wise, the book was only vaguely interesting. Three alien races form an alliance to wipe out humans but the crucial part is that a human scientist to turned traitor and help the races. The Colonial Defense Forces try to implant the scientist's consciousness into an empty body to see if they learn how and why he turned traitor. That's all I'll say without spoiling anything.
I just couldn't get invested in the characters. I didn't care whether the main character (also a white male, like in the first book) lived or died. In fact there were only 2 characters from Old Man's War that were in this book so it feels more like a standalone set in the same universe rather than the second book in a series.