This is an incredibly fun, if not entirely serious, novel. John Scalzi seems to have burst pretty much out of nowhere to produce a pile of onjoyable stuff. The story is action-packed and silly, but reassuringly twisty and inventive. Less dumb than Neal Asher, it feels a bit like early Stross or Stephenson, but tighter and better. I'll avoid spilling the beans on the plot, since you should go read it yourself. Suffice to say, it includes a Scientology parody, which can only help improve things.
The main character is a super-hero, but that's not particularly offensive in a novel of this style. The military background felt disappointingly close to Old Man's War territory, but hey, I'm just not a military sci-fi person. Really these are light criticisms, though, in the context of how much I enjoyed this book. It's the most surprisingly entertaining piece of sci-fi that I've read in quite some time.