This is the first time I've ever thought a sequel was better than the original, and that is no mean feat. What appealed to me about the original (Forge of God) was the way the author told a story and didn't get overwhelmed by sci-fi detail. Even though Anvil of Stars has MUCH more hard science, it refuses to be overwhelmed by technology. This lets the characters and plot stand out. It's believable, interesting and consistent (mostly).
Plot - 4.5 stars - good, creative and for the most part, independent of the first book
Characters - 5 stars - the story describes the life of children who have had no parental guidance for years and are faced with the task of genocide. The are portrayed brilliantly.
Technology - 3 stars - I didn't follow a few of his explanations which led to me not understanding some of the cool stuff.
Setting - 4 stars - Bear chose a neat angle to continue the Forge of God story.
Not all of these are 5 star ratings but to find one book with some much, done so well is wonderful. You wont put it down.