This review applies to the entire trilogy, since it's essentially one giant novel, I'm writing this (and given it 5 stars) since I feel some of the reviews here are not balanced or correct. This trilogy is not perfect, a few problems:
1. The start is slow, and it didn't give the reader a good overview of the technology, economic and political structure of the Confederation (We didn't meet Confederation president until book 2, the working of neural nanonics and the truly destructive power of the antimatter isn't shown until book 3). A lot of the time is spent on a farm planet, which is boring.
2. The bad guy Quinn Dexter is way over the top and annoying with all his insane rambing about God's Brother. It's too convenient that he is the one discovered the Ghost realm and becomes nearly invincible. The good guy Joshua Calvert is also too perfect, good instinct, good piloting, get all the girls, it makes him less human.
3. The aliens are not interesting until much later in the trilogy. In book 1, both Kiint and Tyrathca are like human characters with an alien custome

So for book 1 and 2 I'll probably give 4 stars, however book 3 more than made up for that, it's 5+ with all the interest plots such as:
1. Explore the human side of the possessed
2. Backstabing and power struggle inside the possessed regimes
3. Big space battles and ground attacks
4. A journey to the other side of the Orion nebula with discovery of alien history and culture
5. Various omnipotent alien powers

Overall this is a book with very good and realistic description of future science, technology and society, interesting plots and less than ideal portrait of characters.

Now on to some of the critics of this trilogy:
1. A few people is not satisfied with the ending since it seems that a being with godlike power solved the problem. I don't think this is valid critic:
a. The author already hinted this solution near the end of book 1 and book 2, so it's hardly a surprise.
b. It's not like this is the only solution, there're alternative political and technical solutions in the works
c. The solution didn't come by easily, the main characters have to work hard to reach it in the entire book 3, so I don't feel this is cheating.
d. The scale and seriousness of the problem means it's pretty impossible for a few people to solve it single-handedly, saying the main characters should resolve the problem by their own is just ignorant of how SciFi works. SciFi is not about solving problems, but presenting problems for people to think.
e. The godlike entity didn't actually solve the problem, it gives the main character the power so that he can implement his own solution, thus the idea behind the solution IS Human, it's just the power to implement it comes from outside, it's no different from inventing some super technology to solve the problem.
f. Finally, what happened in the end of book 3 is hardly the full solution of the problem, it solves the immediate crisis and thus gives readers a sense of closure, but problem still exists and requires much more work from the entire human race.

2. Some reviews mentioned science and technical inaccuracies in this book, usually I don't mind these, but in this case accurate description of future science and technology is a strong point of this trilogy, so I think it worths pointing out some of the so called inaccuracies are just misunderstanding of our current science and technology:
a. G force: Someone said ships with 70G+ acceleration and 7G+ turns are unrealistic, well first of all, no where in the book has a human ship pulled 70Gs, that's a Kiint flyer which presumably is far superior to human technology. Human ship with antimatter drive can accelerate at 40Gs, but all the crew is in zero-tau in that case, so it's hardly an error, just creative use of future technology. As for 7G+ turns, today's fighter pilot can endure 9Gs in combat situations, it's not a stretch to think untrained human with genetic enhancement can take 7G+ 600 years in the future.
b. Thermodynamics: A reviewer feels the way the possessed utilize energy violates 1st and 2nd law of thermodynamics, this is just a misunderstanding of these physcial laws. The laws of thermodynamics only applies to a closed system, you can't get energy from nothing, but you can get it from outside the system you're considering. In this case, the possessed is getting energy from some kind of parallel universe, so it's not a violation, actually Asimov explored this in his classic The Gods Themselves.